THE EVOLUTION OF THE PROTEIN PRINCIPLE 241 



and reveal a unifying principle. But this is the history of every 

 discovery in science when viewed in retrospect. The reader of 

 my History of Science will be familiar with numberless instances 

 in point. He will recall that the usual difficulty is that the 

 imagination is hampered by preconceptions of the experimenter 

 based on a false hypothesis of one type or another. 



In the present instance, the hampering hypothesis was the 

 thought that the "substance common to many tissues . . . 

 which has a positive influence in immunity and cure in animals," 

 and even in the alleviation of pain in inoperable cancer in the 

 human subject, is an obscure substance, the method of extraction 

 of which was supposed to be known only to a single individual 

 namely, Dr. Frederick Gwyer, of New York and which was of 

 so problematical a character that the name "X" -substance was 

 given to it. We are told that "the chemistry and method of 

 isolation of this active substance being preeminently the field of 

 Dr. Gwyer, we shall not speak of it." So it appears that the 

 experimenters were working with something -which they regarded 

 as mysterious ; of which, to be sure, they knew the general origin, 

 but regarding the precise methods of preparation of which they 

 were altogether in the dark. 



This was peculiarly unfortunate, both because it savors of an 

 unscientific method of procedure, and because the secrecy in this 

 case probably stood in the way of progress ; for it is hardly con- 

 ceivable that, had the method of extraction employed by Dr. 

 Gwyer been made known to all of the workers, there should not 

 have been some one of them who would have fathomed the open 

 secret, devining, what the originator of the process doubtless 

 himself altogether failed to surmise, that the "X-substance," 

 interpreted in scientific terms, is merely protein, or a product of 

 partial protein hydrolysis. 



But the minds of the operators were under sway of the "X-sub- 

 stance" hypothesis, and hence they were not in the least en- 

 lightened when animal tissues various and sundry were subjected 

 to observation "to see if the 'X'-substance is widely spread in 

 tissues or if limited to the thymus," and were informed that it 

 could be found in a great variety of animal tissues. A table is 

 given, naively showing that Dr. Gwyer has extracted by a 

 method "not yet published" varying quantities of the "X" sub- 

 stance from macerated human embryo, uterine fibroid, chronic 

 cystic masstitis of the breast, and liver of chronic congestion in 

 the human subject ; from muscle, thyroid, thymus, testes, spleen, 

 pituitary, adrenal, and ovary of beef creature ; from carcinoma, 

 heart, stomach, spleen, kidney, sarcoma, lung, liver, intestines, 

 and testes of the rat ; and from fluid from a carcinomatous cyst, 



