14 LIFE : OUTLINES OF GENERAL BIOLOGY 



important constituents, and a corresponding routine of reactions. 

 This is particularly true of the proteins, and there are probably 

 special proteins for each genus at least. There is chemical specificity 

 in the milk of nearly related mammals, such as sheep and goat; 

 and, as (iautier showed in detail, in the gra^x'-juices of nearly related 

 vines. A stain due to the bl<K)d of a rabbit can be readily distin- 

 guished from a stain due to the blcK^d of a fowl or of a man. More 

 than that, as Reichert and Hro\Mi have demonstrated conclusively 

 (iqtK)). the blcHxl of a horse can be distinguished from that of an 

 ass. The cr>-stals of the h.emoglobin or red blood pigment of a dog 

 differ from thos** of a wolf, from which the dog/'volved, and even 

 from those of the Australian dingo, which seems to be the result 

 of domesticated dogs going wild and feral. Even the sexes may be 

 distinguished by their bUxxl, and there are two or three cases 

 among ins<'cts where the colour of the male's blood is different 

 from the female's. The familiar fact that some men caimot eat 

 particular kinds of food, such as eggs, without more or less serious 

 sjTTiptoms. is a vivid illustration of sjxTificity. It looks as if a man 

 was individual not merely in his hnger-prints, but as to his chemical 

 molecules. ICvery maji is his own laboratory. Modem investigation 

 brings us back to the old saying: "All flesh is not the same flesh: 

 but there is one kind of flesh of men, another flesh of beasts, 

 another of fishes imd another of birds." 



We shall return to sjx^cificity in discussing species, but we must 

 emphasise the fundamental fact that the different kinds of animals 

 and plants are very like the chemical elements in their individuality. 

 Each is it.s<'lf and no other. Perhaps the change from one organic 

 t)*])*" to another, a brusque change which we call a large mutation, 

 is comparable to the change from uranium to lead. Perhaps the 

 change from one variety to another, which we call a fluctuation 

 or minor variation, is comparable to the change from one ethyl- 

 compound to another. 



T«) some who have not looked into the matter it may .seem almost 

 prejiostfTous to sjxak of a ])articular protein for every genus at 

 least. Hut the work of Emil Fischer and others has shown that 

 there is inconceivable variety in the groupings and proix)rtional 

 representations of the twenty-odd amino-acids and diamino-acids 

 which constitute in varied linkages the complex protein molecules. 

 There must W a million million ]X)ssibilities and more. As there 

 are alK)Ut 25/hh» named and known .sjxcies of Vertebrates and 

 about 25n.(KK) (some would say 5«k),<m)o) named and known sjxcies 

 of Invert* bratrs. there may readily Ix* particular proteins for every 

 species of animal, having plenty to spare for all the plants. 



GROWTH, MULTIPLICATION, AND DEVELOPMENT.— The 



organism's jv.wer c»f absorbing energy acceleratively, and of accu- 



