there are often other poisons equally dangerous to health."

Physiology.

Macy,

Effect of Alcohol on the Kidneys. - It is said that alcohol is one of the greatest causes of disease in the kidneys. The forms of disease known as fatty degeneration of the kidney" and Bright's disease are both frequently due to this cause. The kidneys are the most important or

66

gans for the removal of nitrogenous waste. Alcohol unites more easily with oxygen than most other food materials, hence it takes away oxygen that would otherwise be used in oxidizing these foods. Imperfect oxidation of foods causes the development and retention of poisons in the blood which it becomes the work of the kidneys to remove. If the kidneys become overworked, disease will occur. Such disease is likely to make itself felt as rheumatism or gout, both of which are believed to be due to waste products (poisons) in the blood.

66

Dr. McMichael, in the Dietetic and Hygienic Gazette, says, Alcohol produces disease of the liver and of the kidneys because these glands are most concerned in the throwing out of any poison, and are always, until they are deranged in structure, engaged in removing it from the body." He further says that the disease almost universally caused in the liver by alcohol is one in which the connective tissue framework of the liver increases, taking the place of the liver cells, until the liver is no longer able to perform its function.

The kidneys may undergo a change similar to that of the liver when alcohol is used, even in moderate amounts, for a long period.

66

Influence of Alcohol upon Excretion. If the waste substances constantly formed in the body are not promptly removed, they tend to poison the system. When the organism is at a high level of health, the breaking down of tissue by oxidation, which produces waste, goes on rapidly and vigorously. When this is retarded, as we have seen it to be when alcohol is introduced into the circulation and uses up the oxygen which should be applied to the oxidation of food, then the weight may increase, but it is by the retention of poisonous matter which ought to be removed. No other one cause creates so much disease of the kidneys as does the use of alcohol. Imperfect oxidation of food develops poisons which the kidneys are overtaxed to remove. This may be caused by eating too much, or by eating unwholesome food, or too much of certain kinds of food, as sugar especially; or it may be caused by alcohol. Fatty degeneration of the kidneys' is a frequent result of the use of alcoholic drinks. The cells of the tissues become so altered, also, that they fail to act normally by removing only the poisonous substances, and they allow the valuable elements in the blood to be drained off with the waste. This is seen in the serious disease called 'Bright's disease' in which the albumin which is necessary to health is excreted by the kidneys." - Macy, Physiology.

Poisons produced by Alcohol. When too little oxygen enters the draft of the stove, the wood is burned imperfectly, and there are clouds

of smoke and irritating gases. So, if oxygen goes to the alcohol and too little reaches the cells, instead of carbonic acid gas, and water, and urea being formed, there are other products, some of which are exceedingly poisonous and which the kidneys handle with difficulty. The poisons retained in the circulation never fail to produce their poisonous effects, as shown by headaches, clouded brain, pain, and weakness of the body. The word "intoxication" means 'in a state of poisoning.' These poisons gradually accumulate as the alcohol takes oxygen from the cells. The worst effects come last, when the brain is too benumbed to judge fairly of their harm. It is not true that alcohol in a small amount is beneficial. A little is too much, if it takes oxygen which would otherwise be available to oxidize wholesome food.

XXVIII. THE NERVOUS SYSTEM AND ORGANS OF SENSE

Problem LV.

A study of the nervous system, reactions to stimuli, and habit formation. (Laboratory Manual, Prob. LV.)

Divisions of the Nervous System.

The control of a number of activities for the attainment of a definite end is the function of the nervous system in the lowest as well as the highest of animals. In the vertebrate animals, the nervous system consists of two divisions. One includes the brain, spinal cord, the cranial and spinal nerves, which together make up the cerebro-spinal nervous system. The other division is called the sympathetic nervous system. The activities of the body are controlled from nerve centers by means of fibers which extend to all parts of the body, there ending in the muscles. The brain and spinal cord are examples of such centers, since they are largely made up of nerve cells. Small collections of nerve cells, called ganglia, are found in other parts of the body. These nerve centers are connected, to a greater or less degree, with the surface of the body by the nerves which serve as pathways between the

end organs of touch, sight, taste, etc., and the centers in the brain

or spinal cord. Thus sensation is obtained.

A nerve cell from the brain of a monkey, showing a great number of tiny protoplasmic projections or dendrites.

or organ of sensation. The axis cylinder process forms the pathway over which nervous impulses travel to and from the nerve centers.

A nerve consists of a bundle of such tiny axis cylinder processes, bound together by a connective tissue. As a nerve ganglia is a center of activity in the nervous system, so a nerve cell is a center of activity which may send an impulse over this thin strand of protoplasm (the axis cylinder process) prolonged into a nerve fiber many hundreds of thousands of times the length of the cell. Some nerve cells in the human body, although visible only under the compound microscope, give rise to axis cylinder processes several feet in length.

Dendrites

Cell Body

Neuraxon

Medulla

Node of Ranvier

-Neurilemma

Nerve-ends

Because some nerve fibers originate in organs that receive sensations and send those sensations to the central nervous system, they are called sensory nerves. Other axis cylinder processes originate in the central nervous system and pass outward as nerve fibers; such nerves produce movement of muscles and are called motor nerves. The Brain of Man. -In man, as in the frog, the central nervous system consists of a brain Diagram of a neuron or and spinal cord inclosed in a bony case with the nerves leaving it. From the brain, twelve pairs of nerves are given off;

nerve unit.

Cerebrum

Cerebellum -

Pons

Medulla

The brain, with parts separated to show each clearly.

HUNT. ES. BIO.-26