590 THE WONDER OF LIFE 



nal variations that miss are not far removed from those 

 that hit, and what misses in one type may hit the mark in 

 another. Constitutional disease is metabolism which 

 has got out of time, out of place, and out of proportion. 

 What is disease in one organism may be normahzed in 

 another. Let us give examples. 



The strange process by which the bone at the base of 

 the stag's antlers dies away every year would be a patho- 

 logical necrosis in other animals, but it has been normahzed 

 in deer and allows the antlers to fall off. The remarkable 

 changes that occur in Ascidian larvae or in tadpoles' 

 tails at the time of metamorphosis would certainly be 

 classed as pathological degenerative processes in other 

 types, but they have been normalized. Similarly, the 

 metamorphosis from the larval to the adult type of archi- 

 tecture is, in many insects, accompanied by inflammatory 

 crises in which phagocytes play an important role. The 

 viscid threads by means of which the male stickleback 

 binds together the leaves of plants to make a nest are pro- 

 duced, according to Mobius, by the enlarged testes affect- 

 ing the kidneys in a semi-pathological manner. There 

 are parallel pathological products in higher animals, but in 

 the stickleback the process has been normahzed, and 

 turned to good account. Do not the sea-swifts, which 

 make snow-white nests of the copious secretions of the 

 mouth, suffer from super-sahvation, and what shall we say 

 of the ' pigeon's milk ' which is formed from a curious 

 degeneration and disruption of the cells Uning the crop ? 



In further illustration of this normahzing of the patho- 

 logical, we may refer to Poyarkoff's description of the 

 gill- plate sacs in which the embryos of the common fresh- 

 water bivalve, Cyclas, are incubated. The embryos 



