324 



Dr. L. T. Hogben and Mr. F. R. Winton. 



By extraction of dried and powdered infimdibulum with acidified water, 

 treatment of the solution with colloidal ferric hydroxide and subsequent 

 continuous extraction of the filtrate at reduced pressure with butyl alcohol, 

 Dudley (1919) succeeded in separating a crystalline residue containing all the 

 uterine stimulant (oxytocic principle) together with a portion of the pressor 

 substance. The latter is again differentiated from the uterine stimulant by 

 the fact that it is rapidly and completely destroyed by boiling with 0*5 per 

 cent. HC1 : on the other hand one-fifth of the uterine stimulant remains after 

 half-an-hour of acid hydrolysis, and at the end of 6 hours a slight trace — less 

 than l/200ths persists. The rapid destruction of the pressor principle was 

 shown by Abel and Nagayama (1920) whose results have been confirmed by 

 Dale and Dudley (1921), and extended as indicated above. There are, 

 therefore, at least two active principles in the extracts of the infundibulum ; 

 and the question thus arises of what relation exists between the melanophore 

 stimulant of the infundibulum and the other pituitary autoeoids. 



The effect of continued acid hydrolysis was investigated as follows. A 

 0"5 per cent, solution of the commercial extract was made up in 0*5 per cent. 

 HC1. This mixture was subjected to continuous boiling for 5 hours, a sample 

 being removed at the end of 30 minutes. At the conclusion of the experiment 

 a sample of the unboiled mixture, the portion which had been subjected to 

 only half-an-hour's hydrolysis, and the residue were respectively neutralised 

 with soda and diluted to a concentration approximately isotonic with Frog's 

 Ringer. From each of the three solutions, A (unboiled), B (boiled half-an- 

 hour), C (boiled 5 hours) - 5 c.c. was injected into a pair of frogs whose 

 pigment cells were fully contracted. The macroscopic and microscopic 

 examination of the six animals at the conclusion of an hour revealed a marked 

 contrast. The A and B pairs were dark and showed the typical pituitary 

 reaction. The pair C remained pale. Microscopic preparations of the skin 

 showed that in the C pair the melauophores were fully contracted, and in the 

 A pair displayed extreme expansion. Those of the B pair were not so 

 extremely expanded as those of the A pair. The result of the experiment 

 indicates that pituitary extracts retain a considerable potency to induce 

 melanophore response after half-an-hour's boiling with 0*5 per cent. HC1. 

 Hence the melanophore stimulant is not identical with the pressor substance, 

 and in its slow destruction by acid hydrolysis behaves in a manner identical 

 with the uterine or oxytocic principle of infundibular extracts, as far as is 

 demonstrable without extensive quantitative estimation of the potency of 

 each sample. 



