CUTANEOUS NEETE-TEEMINATIONS IN MAMMALS. 573 



these hairs, having been torn out, it may be during many suc- 

 cessive generations, became subject to the nov^^ already well- 

 knovs^n phenomena in heredity, and ceased altogether to grow 

 upon their descendants. Athougb, however, the hairs were torn 

 out and subsequently ceased to grow, the hair-follicles, with the 

 nerve-terminal arrangements upon them, remained behind. Con- 

 traction of the empty follicle followed, as a matter of course, 

 when the distending hair no longer existed there ; and so, by gra- 

 dual sbrinking-up into the surface-epidermis of the empty follicle 

 carrying with it the nerve-terminations upon it, we have, as the 

 natural result of this involution of the hair-follicle and its nerves, 

 the evolution of the organ of Eimer. 



It was not merely, however, that the hair-follicle (originally a 

 developmental downgrowth from the epidermis) ceased to grow 

 downwards into the dermis ; for then we should have no right 

 to expect the nerve-terminations peculiar to the hair -follicle to 

 appear upon it. "What we have, then, in the organ of Eimer is 

 really the fully equipped representative of structures that in the 

 fulness of time had acquired complete development, equal to that 

 possessed by them at the present day, on other portions of the 

 body of the same animal, as is seen in fig. 3, Plate XIII., from a 

 hair-foUicle on the tail of the Mole, only half of which has been 

 dravni, in consequence of its large size and the impossibility of 

 including it within one field of the microscope, in order to draw 

 it under a very high magnifying-power. The regular and parallel 

 condition of the forked terminations in that drawing bring one 

 even nearer to understanding the involution which has taken 

 place, than by studying the terminations that appear so irregularly 

 placed in the hair-follicle from the Horse, shown in fig. 7. How 

 the involuted terminations of the nerves on the hair-follicle came 

 to occupy their present precise position within the epidermis we 

 cannot at present explain ; but, as science progresses, we have 

 every hope that every separate phase of evolution between hair- 

 follicle and organ of Eimer will yet be followed and portrayed, 

 it may be on animals belonging to other classes, or upon one and 

 the same animal. 



Another special reason, in addition to the one we have men- 

 tioned, as proving that the hair-follicle and its nerve-apparatus 

 had been fully developed before retrogression took place, is that 

 we believe the organ of Eimer not to be the only form of modifi- 

 cation of the hair nerve-apparatus which exists in the animal 

 kingdom. 



