INERTIA AS RELATED TO HEREDITY 71 



America or Australia may make him somewhat 

 different from the man he was before he set foot on 

 their shores, but never altogether different. The 

 Leopard still cannot " change his spots nor the 

 Ethiopian his skin." By the same property of 

 inertia are preserved various vestigial organs 

 pineal body, appendix vermiformis, membrana 

 nictitans which may be of no use to the possesor 

 and are sometimes positively harmful ; the ease 

 with which the appendix becomes the seat of disease 

 is quite notorious. But by a " blind persistency " 

 they are preserved by functional inertia. By the 

 same property of protoplasm certain evanescent 

 organs are caused to appear in the embryo of each 

 succeeding generation, branchial clefts, coccygeal 

 vertebrae and other anatomical details so familiar 

 to the embryologist. Some are wholly evanescent 

 the branchial clefts, others not ; but every now and 

 again even the mammal exhibits an avian relic, as 

 was the case with a puppy bull-dog born a year or 

 two ago at Shotton, in Flintshire, which had a perfect 

 wing instead of one foreleg. Occasionally, by a 

 still greater display of functional inertia, the foetal 

 type is carried right on into the adult period ; 

 thus the " dog-faced man " of public shows is a case 

 of Hypertrichosis universalis vel Lanuginosa fcetalis. 

 Functional inertia is the mechanism of heredity. 

 The property of protoplasmic inertia in foetal tissues 

 has been appealed toby Professor Adami,* to explain 

 such foetal inclusions as Syncytioma malignum, 



* J. G. Adami, The Clinical Journal, June 18, 1902. 



