Fbbkuaey 14, 1908] 



SCIENCE 



251 



lines of work— such, for example, as have 

 been carried on so successfully in this uni- 

 versity—notably the influence of changing 

 conditions in temperature, oxygen, pro- 

 portion and nature of inorganic salts, etc., 

 as determining factors in fertilization and 

 cell division. Still, the striking peculiari- 

 ties in chemical structure just referred to 

 constantly confront us and call for some 

 logical explanation. 



It has been one of the accepted doctrines 

 of physiology in the past that in the ani- 

 mal body the protein of tissue protoplasm 

 is the result of a simple transformation 

 of the food protein ; digestion in the gastro- 

 intestinal tract leads to the formation of 

 proteoses and peptones, which after ab- 

 sorption are reconverted into such proteins 

 as are adapted to the needs of individual 

 organs and tissues. Latterly, however, 

 this view has been steadily losing ground. 

 The discovery of the enzyme erepsine in 

 the intestine of man and the higher ani- 

 mals, together with its well-established 

 power of quickly breaking down peptones 

 into crystalline fragments, among which 

 the diamine acids stand out conspicuously, 

 has raised the question whether in the in- 

 testine prior to absorption food protein is 

 not more or less completely disintegrated 

 with formation among other fragments, of 

 arginine, lysine and histidine, out of which 

 in the liver or elsewhere specific proteins 

 are manufactured de novo to meet the 

 needs of the individual organism. There 

 are many grounds for attaching consider- 

 able weight to this view, although the ques- 

 tion is by no means settled. The facts, 

 however, point clearly to the probability 

 that in digestion the food protein is more or 

 less broken down into amino acids and 

 very simple peptides, and if the organism 

 is to derive advantage from these nitrog- 

 enous fragments for the manufacture of 

 protein to make good tissue waste, then 

 synthesis must be the rule. Further, it is 



easy to see how by such a method of pro- 

 cedure the animal body is able to construct 

 by a proper selection of these fragments 

 the specific proteins needed by different 

 types or species of organisms; far more 

 easily, indeed, than if the changes under- 

 gone by the varying food proteins during 

 digestion are limited to such slight trans- 

 formations as are involved in peptoniza- 

 tion, etc. Assuming this view to be cor- 

 rect, we see a close analogy between the 

 construction of body protein in ordinary 

 nutritive processes and the synthesis of 

 protein in those phases of growth and de- 

 velopment associated with fertilization and 

 cell division. In both cases, diamine acids, 

 notably arginine, lysine and histidine, are 

 conspicuous elements, but it is to be noted 

 that in the spermatozoon nucleus the pro- 

 tein part of the nucleoprotein is character- 

 ized by great simplicity of structure and 

 with a dominance of diamino acids, notably 

 conspicuous in the protamines, less so in 

 the histones. As constrasted with the pro- 

 teins of somatic cell nucleoproteins, the 

 difference is very striking and must have 

 some significance. The latter are rela- 

 tively very complex; a complexity which 

 shows itself in a far larger number of 

 building stones, monoamine acids, etc., 

 with a corresponding diminution in the 

 proportion of diamino acids, such as 

 arginine. We can well conceive that in 

 fertilization and the subsequent nuclear 

 changes which precede rapid cell division 

 there must be some inciting element, some 

 conditions prevailing other than those 

 which characterize the somatic cells, and it 

 would seen justifiable to ask if this pecul- 

 iar chemical structure of the spermatozoon 

 protein, with its high content of diamino 

 acids, may not be in some measure respon- 

 sible for the characteristic reactions that 

 accompany and follow fertilization. It is 

 certainly a conspicuous fact that the sperm 

 nucleus of many species of animals eon- 



