On the other hand, when the diet is faulty in certain respects, the nervous system is profoundly affected. This is perhaps most pronounced with diets deficient in calcium or in phosphorus. Inadequacy of the protein of the diet is also capable of causing irritability and nervousness. We have observed a group of rats which had been restricted during growth, to a diet in which the sole protein content was 6 per cent, half of which was derived from maize and half from peas. They were very apprehensive of danger and would retire in alarm when the cage was opened. Well nourished animals do not become alarmed under such conditions.

In extreme cases, young rats which are restricted for a few weeks to such deficient diets become extremely nervous and irritable. When the cage is opened they may retreat as far as possible and sit upon their haunches or crouch in an attitude betraying great alarm, and squeal when an attempt is made to pick them up with tongs. One would certainly be bitten if one were so rash as to attempt to take them in the bare hands. It is often difficult to seize them by a foot or by the tail by means of tongs because of their frantic springing about. They even leap out of the cage past their would-be captors. Normally nourished rats can be placed in a box together and transported to the balance for weighing, without arousing any excitement. When the box is temporarily uncovered they do not evince a desire to escape. The nervous ones, made timid by faulty nutrition, under these circumstances jump about frantically and make violent efforts to escape the instant that a ray of light is admitted to the box. Not infrequently we have corrected the diets of animals in this condition of nervous instability and have been able within three or four weeks, to pick up the entire group of five or six with one bare hand without causing them any unrest.

There are in our experience all gradations of nervous instability between these extremes. Some behave so as to cause an entry in the note-book that they are "wild," but never reach an extreme degree of timidity. Many times we have observed young rats nourished by mothers whose diets were deficient in calcium, to develop typical symptoms of tetany. They would appear to be well nourished up to the seventeenth or eighteenth day of nursing, then would suddenly develop a paroxysm. These seizures were experienced at intervals for some hours when death resulted. Timidity and nervousness are also characteristic of many rats whose diets are deficient in the anti-neuritic substance.