470 SECRETION". 



more reliable and satisfactory. In a number of analyses of the livers of dogs confined 

 to different articles of diet, Pavy found a little over seven per cent, of glycogenic matter, 

 upon a diet of animal food ; over seventeen per cent., upon a diet of vegetable food ; and 

 fourteen and a half per cent., upon a diet of animal food and sugar. These results have 

 been confirmed by M'Donnell, who, in addition, found that hardly a trace of amyloid 

 substance could be detected in the liver upon a diet of fat, and none whatever upon a diet 

 of gelatine. Bernard had already observed that the amount of sugar produced by the 

 liver upon a diet of fat was the same as during total abstinence from food. These facts are 

 entirely in accordance with observations upon the effects of different kinds of food in 

 diabetes, and they have an important bearing upon the dietetic measures to be employed 

 in this disease. 



The effect of entire deprivation of food is to arrest the production of sugar in the 

 liver, three or four days before death. This arrest of the glycogenic function has gener- 

 ally been observed in cases of disease, except when death has occurred suddenly. 



Influence of the Nervous System, etc. Bernard has studied the influence of the ner- 

 vous system upon the production of sugar more satisfactorily than any other of the vari- 

 ations of the glycogenic function, for the reason that he has noted these 

 modifications by determining the sugar in the blood and in the nrine. 

 Some of the points with regard to the nervous system we shall consider 

 again, and it is sufficient, in this connection, to mention the main results 

 of some of the most striking of the experiments upon this subject. 



The most remarkable experiment upon the influence of the ner- 

 vous system on the liver is the one in which artificial diabetes is 

 produced by irritation of the floor of the fourth ventricle. This 

 operation is not difficult, and it is one that we have often repeated. 

 The instrument used is a delicate stilet, with a flat, cutting extremity, 

 and a small, projecting point about ^ of an inch long. In perform- 

 ing the operation upon a rabbit, the head of the animal is firmly 

 held in the left hand, and the skull is penetrated in the median 

 line, just behind the superior occipital protuberance. This can easily 

 be done by a few lateral movements of the instrument. Once with- 

 in the cranium, the instrument is passed obliquely downward and for- 

 ward, so as to cross an imaginary line drawn between the two auditory 

 canals, until its point reaches the basilar process of the occipital bone. 

 The point-then penetrates the medulla oblongata, between the roots of 

 the auditory nerves and the pneumogastrics, and, by its projection, 

 serves to protect the nervous centre from more serious injury from the 

 cutting edge. The instrument is then carefully withdrawn, and the 

 operation is completed. This experiment is almost painless, and it is 

 not desirable to administer an anaesthetic, as this, in itself, would dis- 

 turb the glycogenic process. The urine may be drawn before the oper- 

 ation, by pressing the lower part of the abdomen, taking care not to 

 allow the bladder to pass up above the point of pressure, and it will be 

 found turbid, alkaline, and without sugar. In one or two hours after 

 the operation, the urine will have become clear and acid, and it will react 

 FIG. 140. instru- readily with any of the copper-tests. When this operation is performed 

 without injuring the adjacent organs, the presence of sugar in the urine 

 O10i}y tem P rai T> and the next day the secretion will have returned 

 to its normal condition. It is best, in performing this experiment, to 

 operate upon an animal in full digestion, when the production of sugar is at its maximum. 

 The production of diabetes in this way, in animals, is exceedingly interesting in its 

 relations to certain cases of the disease in the human subject, in which the affection is 



