514 DIGESTION. 



ganglion. Thence they proceed in the gangliated cord of the 

 sympathetic and the splanchnic nerves to the liver. When 

 these vasomotor fibres are severed, -either by dividing the 

 fibres on the vertebral artery or those forming the annul us of 

 A'ienssens, or by extirpating the third cervical or first dorsal 

 eanjrlion, the hepatic vessels dilate, and diabetes occurs. It 



is of great importance to notice that section of the sympa- 

 thetic cord or the splanchnic nerves does not produce diabetes, 

 although the vasomotor nerves of the liver are thus divided. 

 The reason of this probably is that the vasomotor nerves of 

 the intestine, being divided at the same time, so much blood 

 goes to the inte&tina] vessels that the circulation in the liver 

 is not increased. The vessels can be dilated reflexly by irrita- 

 ting the central ends of the cut vagi, or the roots of the vagus 

 in 'the fourth ventricle. Section of the splanchnics or sym- 

 pathetic cord prevents the occurrence of diabetes when the 

 fourth ventricle is afterwards punctured, but does not remove 

 it when already present. Diabetes may also be produced by 

 the inhalation of carbonic oxide (Schmiedeberg), chloroform, 

 or nitrite of amyl, or by the injection of curare. As regards 

 carl ionic oxide, it has been ascertained that the action is not 

 prevented in the. dog by section of both splanchnics, but in 

 rabbits it does not produce diabetes at all (Eokhard). 



Increased proportion of sugar in the blood determines glyco- 

 suria. To show this, expose the jugular vein in a healthy rab- 

 bit, having first weighed it and ascertained that its urine is free 

 from sugar. Then slowly inject 5 to 10 per cent, solution of 

 grape sugar into the vein. About two grammes of sugar should 

 be used for every kilogramme of body weight. Sugar is found 

 in the urine shortly after, but next day it will have disappeared. 

 It has been found that if the amount of sugar in the blood does 

 not exceed a half a gramme for each kilogramme of body weight, 

 it 'may not appear in the urine. 



** 162. Production of Glycosuria "by Puncture of 

 the Floor of the Fourth Ventricle. The part of the 

 fourth ventricle the puncture of which is followed by the most 

 abundant appearance of sugar in the urine is limited superiorly 

 by a line joining the origin of the auditory nerves, and inferi- 

 orly by one joining the origins of the vagi ; a puncture higher 

 up. or to either side, may, however, produce more or less glyco- 

 suria. It has been ascertained by Bernard that it is essential 

 to the result, that the olivary fasciculi should be injured, and 

 th..t it is not produced by injury of the superficial, i. e., poste- 

 rior sensory layers. The instrument used for puncturing the 

 ventricles consists of a small steel chisel (see Fig. 315), about 

 four millimetres broad, and having a style in the middle winch 

 projects about two millimetres beyond the cutting edge. This 

 chisel is pushed on through the occipital bone and the cere- 



