EMBRYOLOGY AXD MEDICAL PROGRESS 13 



history of their own throughout the embryonic period and do not 

 contribute in any way to the formation of any of the organs of the 

 body. Since then Mr. B. M. Allen has discovered that the history of 

 the germ-cells in the turtle is strikingly similar, and Dr. Woods is 

 now engaged in tracing out the history in birds. Every one present 

 will, of course, immediately recognize the great importance of a dis- 

 covery which tends to show that there is a permanent distinction be- 

 tween the reproductive cells and the somatic cells which belong to the 

 body and do not serve for reproduction. 



Concerning cytomorphosis I need not add anything to what has 

 been said concerning its general value in pathological study, but I 

 should like to refer briefly to the good results which we may anticipate 

 from direct application of the notions supplied by embryologists to 

 the investigations which are yet to be made upon what we may call the 

 morphological diseases, in distinction to those which are of parasitic 

 origin. Morphological diseases arise through intrinsic causes, ab- 

 normal conditions due to the body itself and its reactions. Parasitic 

 diseases have extrinsic causes. The dramatic — I misdit almost say 



*o 



melodramatic — growth of bacteriology and the kindred sciences has 

 caused us to give most of our attention to diseases of the infectious 

 type caused by some vegetable or animal parasite. This tendency is 

 to be so far regretted that it has rendered investigation one-sided and 

 lured it away from the class of diseases which may be attributed to 

 pathological cytomorphosis. In regard to these the fundamental 

 problem is identical for the pathologist and embryologist. It is the 

 question of what and how the change in the structure of the single 

 cell may be. Here is a central problem about which a vast number of 

 lesser problems revolve like satellites. In the solution of this and of 

 allied problems our greatest hopes for the future progress of medicine 

 seem to lie. If we can find out what are the conditions which cause a 

 cell to change its structure and advance in its cytomorphosis, we may 

 hope that that discovery will include the explanation of why certain 

 cells develop abnormally and become, as we commonly say, pathological, 

 and we are to have precise knowledge of the cytomorphic causes we 

 may dare, even now, to hope that we shall learn to regulate them, and 

 that some, at least, of the diseases which are now beyond our reach 

 will come under our control. It was not long ago that the idea of 

 conquering diseases like malaria, yellow-fever, diphtheria and tuber- 

 culosis seemed a mere dream, a beautiful dream, yet control of them 

 is now a reality, and is becoming almost daily more assured, complete 

 and beneficent. So too in regard to the strictly morphological dis- 

 eases, knowledge may bring mastery; and even sclerosis, that disease 

 from which we are all assumed to be suffering in varying degrees, may, 

 ere long, find itself subject to man. 



Of the services which embryology has rendered to medical science 



