378 A MANUAL OF PHYSIOLOGY 



stimulation of the chorda. See whether the sympathetic is also 

 inactive, and report the result. 



(2) Now empty the cannula in the submaxillary duct by means of 

 a feather, and fill it with a 2 per cent, solution of pilocarpine nitrate 

 by means of a fine pipette. Fill also the short rubber tube attached 

 to the cannula, and close it with a small piece of glass rod or a pair 

 of bulldog forceps. Compress the tube, and so force into the duct 

 a small quantity of the solution. Open the tube. Secretion of saliva 

 will again begin, and stimulation of the chorda will again caure an 

 increase in the flow. But after a few minutes the action of the 

 atropia will reassert itself and the flow will stop. Renewed secretion 

 may be caused by a fresh injection of pilocarpine. 



4. Gastrio Juice. (a) Preparation of Artificial Gastric Juice, 

 Take a portion of the pig's stomach provided, strip off the mucous 

 membrane (except that of the pyloric end), cut it into small pieces, 

 with scissors, and put it in a bottle with 100 times its weight of 

 0*2 per cent, hydrochloric acid. Label and put in a bath at 40 C. 

 for twelve hours. Then filter. 



(b} Take another portion of the mucous membrane, cut it into, 

 pieces, and rub up with clean sand in a mortar. Then put it in a 

 small bottle, cover it with glycerine, label, and set aside for two or 

 three days. The glycerine extracts the pepsin. 



(c) Take five test-tubes, A, B, C, D, E, and in each put a little 

 washed and boiled fibrin. To A add a few drops of glycerine 

 extract of pig's stomach, and fill up the test-tube with 0*2 per cent, 

 hydrochloric acid. To B add glycerine extract and distilled water ; 

 to C glycerine extract and i per cent, sodium carbonate ; to D 

 0*2 per cent, hydrochloric acid alone ; to E glycerine extract which 

 has been boiled, and o'2 per cent, hydrochloric acid. 



Put up another set of five test-tubes in the same way, except that a 

 few drops of a watery solution of a commercial pepsin are substituted 

 for the glycerine extract. Label the test-tubes A', B', C', D', E'. 



Into another test-tubs put a little fibrin, and fill up with the 

 filtered acid extract from (a). Label it F. Place all the test-tubes 

 in a tumbler, and set them in a water-bath at 40 C. 



After a time the fibrin will have almost completely disappeared in 

 A, A', and F, but not in the other test-tubes. Filter the contents of 

 A, A', and F into one dish. 



(d) Test the filtrate for the products of gastric digestion : 



(a) Neutralize a portion carefully with dilute sodium 

 hydrate. A precipitate of acid-albumin may be 

 thrown down. Filter. 



(/?) To a portion of the filtrate from (a) add excess of 

 sodium hydrate and a drop or two of very dilute 

 copper sulphate. A rose colour indicates the 

 presence of proteoses or peptones. The cupric 

 sulphate must be very cautiously added, because aa 

 excess gives a violet colour, and thus obscures the- 

 rose reaction. If still more cupric sulphate be 

 added, blue cupric hydrate is thrown down, and 



