49 8 SCIENCE PROGRESS. 



for free hydrochloric acid. It is easily soluble in water or 

 glycerine. The watery solution gives a pp. on cooling to 

 o° C. and coagulates on heating to 6o° C. It digests pro- 

 teids readily. The active body, or pepsin, can also be 

 obtained from gastric juice by saturation with ammonium 

 sulphate, as Kuhne has already pointed out. The pepsin 

 obtained in this way agrees very closely with that obtained 

 on cooling the gastric juice, as is shown by the subjoined 

 elementary analysis of two samples of pepsin obtained in 

 these two different ways. 



Pepsin Precipitated by Cold. Pepsin Precipitated by Am, S0 4 . 



Carbon, - 5°'73 per cent. 5°"37 per cent. 



Hydrogen, 7-23 „ 6-88 



Chlorine, - 1*17 and i'oi ,, o - 8a and 0*89 ,, 



Sulphur, - 0-98 „ 1-35 and 1-34 



Nitrogen,- „ 14-55 and l S'° 



We have now to inquire what is the path of the reflex 

 from the nervous centres to the stomach. If both splanchnics 

 be divided in one of the dogs with gastric and oesophageal 

 fistulse, the dog after an attack of diarrhoea returns to a 

 practically normal condition. Under these circumstances, it is 

 found that the sham feeding is followed, as in the case of 

 normal dogs, by a copious secretion of gastric juice. It is 

 evident that the splanchnics do not carry the efferent im- 

 pulses of the reflex act. The next step w r as to divide both 

 vagi, and here certain precautions were necessary. Division 

 of both vagi in the neck causes paralysis of the larynx and 

 oesophagus, and death after two or three days from 

 pneumonia. To avoid this catastrophe, Pawlow proceeded 

 in the following manner : On one day in the anaesthetised 

 animal, the gastric fistula was instituted, and then the right 

 vagus exposed low down in the neck by an incision outside 

 the sternomastoid, and divided below the subclavian artery, 

 i.e., below the point where it gives off its recurrent branch. 

 The operations were of course performed with strict aseptic 

 precautions, and the animals recovered rapidly. When 

 they were quite well the double oesophageal fistula was 

 made. A few days later, after recovery from the second 

 operation, the animal was placed in a special holder made 



