tains (a natural subdivision of the more important articles treating the San Gabriel Mountains) of southern section Capillaria of genus Panicum California has been prepared by (ibid., 110) and the common raspJohnston (Plant World, xxii, 71). berry (ibid., 89), of which five varieContinuing his notes on new and note- ties and some additional forms are worthy Philippine plants, Merrill recognized, only one variety being (Philippine Jour. Science, C. Bot., new. The discrepancy between the xiii, 263) describes 84 new species, taxonomic and the morphological syswidely distributed in the various fam- tems in plant classifications is critilies. The same author publishes ically discussed by Conard (Plant notes (ibid., 123) on the flora of Loh World, xxii, 59), who offers a tabulaFau Mt., Kwangtung, China, from tion of orders and families for "muwhich it is apparent that the southern tual readjustment." The practical portion of China is entirely inade- importance of the quadrat method of quately explored. He has also com- Clements in studying vegetation is pleted (ibid., 67) the descriptions of urged by Weaver (Plant World, xxi, new species of Bornean plants prelim- 267) as a check on superficial generalinary to the publication of a "biblio- izations by the student worker. graphic enumeration" of the Bornean flora. Continuing a report of the phytogeography of the Rocky Mountain region (Bull. Torrey Bot. Club, lxvi, 295) Rydberg treats in this paper the distribution of montane plants, and for the purpose divides the northern Rockies (northward of Wyoming) into eight districts and the southern Rockies (extending from the latter to northern New Mexico) into four districts. Of the 1,900 species found, less than 13 per cent. are transcontinental, and including the latter the number of species common to the Rockies and to the Pacific mountains is about 43 per cent.

The most extensive taxonomic monograph of the year is Volume 1 of a report on the Cactaceae by Britton and Rose (Carnegie Inst., Wash., Publ. No. 248, 1). This report covers the tribe Pereskieae and to a large extent the tribe Opuntieae. The work is copiously illustrated, and it is intended to make a complete investigation of the family, not limited to American species. Fernald (Rhodora, xxi, 1) maintains the desirability of treating in a broad way the genus Arenaria with the elimination as genera of several proposed segregates. He (ibid., 41) reviews the distribution of Pinus Banksiana and Thuja occidentalis, reviving the discussion of the importance of the presence or absence of lime in plant distribution. Many additional notes have been published upon the New England flora, some of the

Studying the embryo and seedling of Dioon spinulosum, a cycad unique in appearance, with an ovulate strobilus of great size, Sister Dorety (Bot. Gaz., lxvii, 251) finds that the cotyledons vary from two to four in number, but the vascular strands of all the plant members differ in no marked degree from the general cycad arrangement. The Living Cycads (Univ. of Chicago Press) is a small book by Chamberlain which endeavors to present for the teacher and general reader the results of the author's wide experience in the field and laboratory. with this group of tropical and subtropical plants.

In a very readable article Berry (Plant World, xxi, 284) discusses the geologic history of four leguminous trees, namely, locust (Robinia), honey locust (Gleditsia), the Kentucky coffee tree (Gymnocladus), and the Judas tree or red bud (Cercis), all belonging to the bean family (Papilionaceae), which is relatively young geologically, having attained maximum variation since the beginning of the Pleistocene glaciation. Berry (Bull. Torrey Bot. Club, xlvi, 285) also describes a new Matonidium from Colorado. This genus, together with the allied Laccopteris, usually regarded as related to the living family Cyatheaceae, has closer affiliations with the existing genus Matonia, the latter occurring in the Malay Peninsula and in Borneo. Matonidium is distributed in both hemispheres.

PHYSIOLOGY AND PHARMACOLOGY
S. J. MELTZER

Shock. Although shock ceased to be an urgent practical problem since the signing of the armistice in November. 1918, scientific interest in the subject has not ceased. An extended review of investigations of the shock problem and of theories of shock was given in the YEAR BOOK for 1918 (pp. 697-701). The physiological literature of the year 1919 contains numerous articles on shock, many of which will have to be noted in the present review of physiology and pharmacology (see also Medicine, and Surgery, infra).

Erlanger, Gesell, and Gasser, (Am. Jour. Physiol., xlix, 90) produced shock by exposure and handling of the intestines and studied the course of arterial and venous (systemic and portal) blood pressures and the peripheral resistance. Peripheral resistance is in inverse proportion to the venous blood pressure. A fall of arterial blood pressure to 50 mm. Hg was taken as an indication of the presence of shock. Their results, briefly stated, were as follows: Arterial pressure may at first be slightly lowered. After some time the pressure begins to fall and continues to fall more or less steadily. The average time for coming down to 50 mm. is about four hours. The fall in the systemic venous pressure is insignificant. Portal venous pressure, however, falls continuously through the first two or three hours; it then ceases to fall or actually rises slightly until the arterial pressure has reached a comparatively low level, when the portal pressure again begins to decline. The peripheral resistance, both somatic and splanchnic, is increased at first, but at about the time the arterial pressure starts on its steady decline, the peripheral resistance begins to diminish, and by the time the

arterial pressure has reached 50 mm. Hg the peripheral resistance is below normal. But up to the time of death the vessels preserve some residual tone, and the vaso-motor center shows some slight reactivity. A considerable loss of fluid from the exposed bowel occurs as a result of transudation through the serous surface. The initial changes in the circulation can thus best be explained upon the assumption that the effective blood volume is reduced.

Erlanger and Gasser (ibid., 151) studied by their methods the effects of temporary anæmia induced by partial occlusion of the vena cava (Janeway and Jackson) and by temporary obstruction of the aorta. With reference to the vena cava, Janeway and Jackson produced the occlusion by placing a thread upon the cava in the thorax, whereas Erlanger and Gasser compressed it between liver and diaphragm by means of a graded clamp. The results were practically the same, except that Janeway and Jackson state they obtained shock after 18 hours, whereas Erlanger and Gasser obtained it in a much shorter time, at an average of about five hours. They divide their experiments in two groups. In the first, larger group, while the cava is occluded, the rise in the venous pressure causes blood to accumulate in the veins, both systemic and portal, and the arterial pressure consequently falls. The vasomotor center, stimulated by the anæmia thus produced, immediately calls forth peripheral constriction, but later the anæmia begins to tell on the center and its tone begins to give way. The moment at which this change takes place the tone is increased. The effective blood pressure, that is, the difference between the arterial and

a

venous pressure, is relatively large; temic venous pressure either was not the flow of blood, therefore, is rela- altered or fell, and that the portal, tively free. When the cava is un- pressure rose and remained at a high clamped within a few hours, the level. Bainbridge and Trevan be: arterial pressure rises at once lieve that the shock in their experiabruptly and then more and more ments was brought about by the obslowly, but sooner or later, in less struction of the flow of blood than an hour or two, the pressure through the liver. Erlanger and begins to decline, which leads to Gasser (ibid., 345) repeated many death in the course of some hours. experiments of Bainbridge and TreIn the second group occlusion of the van and gained considerable inforcava caused some elevation of the mation bearing upon the so-called systemic, and an enormous elevation shock-producing action of adrenalin, of the portal, venous pressure, which and upon the action of massive doses causes a marked reduction of the of adrenalin in general. In the effective blood pressure. Evidently course of their investigations they this reduction in the effective blood were led to study the effect upon the volume is the factor that accounts for circulation of injecting into the portal the lower arterial blood pressure. At vein toward the liver a suspension of autopsy the mucosa of the small in- lycopodium spores and thus interpostestine is usually of a deep bluish ing a high resistance to the passage red, and the capillaries and the of the blood through the liver. Their venules of the villi are almost in- results are as follows: With regard variably enormously distended and to the action of adrenalin, it may be solidly packed with red corpuscles. said that in general they confirm the The aorta was partially occluded in statement of Bainbridge and Trevan, the chest just beyond the origin of namely, that a prolonged injection the left subclavian artery. In these leads to a shock-like condition in experiments, therefore, the blood sup- which the venous systemic pressure ply to the upper part of the body was shows no constant alteration, whereas not diminished. The fall of arterial the portal pressure is markedly inpressure to the level of 50 mm. in creased during the injection and may these experiments is due to a reduc- remain high subsequently. At the tion in the effective volume of blood. same time they present evidence that The gross lesions found in these ani- accumulation of blood in the portal mals were the same as in the animals area as a result of the increased porwith venous occlusion. The striking tal hepatic resistance is not in itself changes in both kinds of animals is the cause of the failure of the circulathe tremendous distention of the tion; for marked obstruction of the capillaries and venules of the intesti- hepatic radicals in the liver by the nal villi with solid masses of red injection of a suspension of lycopo corpuscles. Erlanger and Gasser dium spores may not lead to the conclude from their experiments (1) shock-like failure of the circulation that the failure of the circulation that is seen after adrenalin. Erlanafter both manipulations is in part ger and Gasser believe that the failure due to the consequences of "sequestra- of the circulation is to be attributed tion" of corpuscles in the capillaries to the extreme slowing of the blood and venules, and (2) that the back flow throughout the body caused by pressure in the veins is not an es- the constricting action of adrenalin sential factor in the production of shock.

on the arteries. They come to the conclusion that the cause of the cirBainbridge and Trevan stated that culatory failure brought about by shock can be produced in animals by adrenalin is the same as after temthe continuous injection of adrenalin porary partial obstruction of the for 20 minutes at such a rate as to vena cava or of the aorta. This conkeep the arterial pressure up to that clusion seems to be justified by the attained by moderate stimulation of fact that the most striking lesion sensory nerves. They found that dur- found in animals dying as a result of ing the injection the arterial pressure any of these three procedures is alike; rose to a high level, that the sys- it consists in a tremendous engorge

ment of the capillaries and venules of the villi of the intestines.

initial threshold is the same in both. The rise of the threshold brought about by intestinal manipulations in decerebrated animals may possibly be a phenomenon of inhibition.

even under a very deep state of anesthesia in which stimulation of the central end of the vagus and the respiratory center do not react to CO2, the stimulation of the inhibitory nerves of the respiration (central end of the laryngeal superior or vagus nerves) respond promptly with inhibition of respiration which may lead to the death of the animal. Mann is inclined to look upon this action of ether as an increase of the inhibitory function of the respiration (Meltzer). Second, all the tissues of one leg were ligated except the corresponding artery. The removal of the ligature was followed by manifestations of shock symptoms. Mann assumes that the shock-like manifestations are brought about by the absorption of toxic substances from the abused tissues of the ligated leg.

In Gesell's studies (ibid., xlvii, 468) shock is considered in a very general way as a combined circulatory and nutritional disturbance resulting In his studies on experimental surfrom a number of forms of tissue gical shock Mann (ibid., 231) brings abuse, which, if left to run their out two points of interest. First, course, may lead to death. Gessell divides the causes of shock into initiating and sustaining factors and lays a great deal more stress upon the volume flow of blood in shock than upon the mean blood pressure. The two do not have a parallel course; for instance, a reduction of volume flow amounting to 85 per cent. of the initial flow may occur with a constant head of pressure or with a small change in head of pressure, a rise as well as a fall. The sudden decrease in volume flow may after a time be as suddenly checked; with a further fall in pressure the flow may for a time remain constant, decrease, or even increase. The intial decrease in volume flow far exceeds that occurring during the subsequent fall of pressure to zero. Gesell compared further the effects of hemorrhage with that of tissue abuse. Hemorrhage and tissue abuse have many points in common, but there are also clear points that distinguish the two conditions. Hence, similar principles of treatment with certain modifications may be applied to hemorrhage and to shock.

E. L. Porter (ibid., 208) studied the effect of primary shock produced by drawing out the intestines and manipulating them with the fingers upon the thresholds of flexion and of crossed-extension in decerebrated cats. Flexion threshold reflex is raised by intestinal manipulations; the rise begins very promptly, but it returns to the initial threshold upon the cessation of the manipulation. (The rise often fails-11 times in 24 experiments.) The rise in the threshold is not due to low blood pressure; flexion threshold rise often coincides with a rise in blood pressure, and the return of the threshold to the initial state often occurs while the blood pressure continues to fall. The rise of the crossed-extension threshold is much greater than the rise of the flexion threshold. The return to the

Stewart and Rogoff (ibid., xlviii, 22) studied the output of adrenin in shock. There are statements in the literature to the effect that in conditions of shock the output of adrenin is much increased. In some cases it may be even more than 32 times the initial output. Stewart and Rogoff think that these statements are based upon faulty experimentation. In their own studies they found that the rate of output of adrenin in dogs and cats after the blood pressure had been permanently lowered by exposure and manipulation of the intestines, by partial occlusion of the inferior vena cava, by hemorrhage, and by "peptone" injection, was the same as before the lowering of the blood pressure.

Gasser, Erlanger, and Meek (ibid., 1, 31) studied blood-volume changes and the effect of gum acacia upon their development in shock brought on by injections of adrenalin, by clamping the aorta or the vena cava and by exposure and manipulation of the intestines. They found that the blood volume was decreased in all forms of experimental shock and after

all grades of damage. The effective | sodium bicarbonate did not affect the volume of the blood may be reduced mortality, or rather increased it either by dilatation of the capillaries slightly. They finally found that a and small veins with greatly de- solution consisting of 25 per cent. gum creased slowing of the circulation or acacia in 18 per cent. glucose given as the result of transudation of 5 cc. per kilogram of body weight an plasma, or transudation of plasma hour proved to be the most favorable and jamming of the corpuscles in the mixture. Under the administration capillaries and venules, or the latter of this mixture the mortality decombined with absolute stasis in some creased to 24 per cent. within 48 part of the vascular system or by hours. They believe that their rehemorrhage into the tissues, especially sults indicate that bicarbonate and into the lumen of the intestines. the high viscosity of a strong acacia They found further that the transuda- solution are somewhat harmful in tion of plasma is greatly opposed by traumatized animals; that the injection of 4 cc. per kilogram of 20 harmfulness of the strong viscid gum per cent. acacia before traumatization. can be avoided in part through the In the foregoing experiments two osmotic action of hypertonic glucose facts were brought to light, namely, subsequently injected but not by bithat a decrease of blood volume is an carbonate; and that when hypertonic essential factor in all forms of shock, gum and the hypertonic glucose are and that an intravenous injection of given simultaneously and slowly so as a concentrated solution of gum acacia to avoid altogether the period during tends to prevent the concentration of which the high viscosity of the gum the blood. These facts induced is hampering the circulation, a maxiGasser and Erlanger (ibid., 104) to mum saving of life can be effected. study the best means for restoration Erlanger and Gasser (Ann. Surg., of the plasma volume. Their experi- Ixviii, 389) report that their mixture ments led them to the following re- was employed in 11 men with a favorsults. When glucose in 18 per cent. able result. solution is injected into the circulation of a normal animal, the blood returns to its normal circulation within five to 45 minutes. When gum acacia in a concentrated solution is injected, the decline of the blood volume to normal requires 22 to six or more hours. When the concentrated acacia is immediately followed by an injection of glucose, the effect is much greater than that resulting from the injunction of either of the two substances alone. Comparable results were obtained in animals in shock when a strong solution of gum acacia is followed by a solution of Blood Coagulation.-Recent work Na, CO, which is isosmotic to 18 per on blood coagulation indicates that at cent. glucose. This mixture offers least six different substances are conthe advantage that it sustains the cerned in this process, namely, alkali reserve. In a statistical study fibrinogen, thrombin, prothrombin, of the treatment of measured trauma calcium, antithrombin, and thromboErlanger and Gasser (ibid., 119) plastic substances. As to the last sought to establish the most favorable mentioned factor, evidence has been mixture of solutions of gum acacia obtained to show that the active maand crystalloids. They employed the terial in tissue extracts is a phospartial occlusion of the inferior vena phatid (cephalin). According to cava as the standard damage. Forty- Howell and Holt (ibid., xlvii, 328), eight per cent. of untreated animals two more substances have to be added died within 48 hours. The adminis- to the list of fibrin factors. The two tration of mixtures of acacia with new substances are designated heparin

Mann (Am. Jour. Physiol., 1, 86) has an article on the treatment of the condition of low blood pressure that follows exposure of the abdominal viscera. Experimentally he found that heat is useful, rebreathing was of no importance, and none of the drugs usually employed in the treatment of shock was very effective. The best results were obtained from injection of fluid media. The data of his experiments justify the conclusion that none of the artificial solutions gives such good results as the use of blood.