1 7 6 



THE HUMAN SPECIES 



other mammals the globe is spherical ; speaking roughly, it is so 

 in the cheiroptera, apes and man (see Fig. 87). Strictly it is an 

 ellipsoid on to whose anterior aspect a segment of a smaller 

 sphere has been attached. 



The presence of lymphoid follicles in the palpebral con- 

 junctiva is characteristic of the domestic animals (man does not 

 possess them) ; they are specially numerous towards the inner 

 canthus at and in the neighbourhood of the transitional fold of 

 conjunctiva (plica semi-lunaris) over the palpebra tertia (nicti- 

 tating membrane). 1 This 

 semi-lunar fold of conjunc- 

 tivapresent in fishes 

 (shark), in amphibia (rep- 

 tiles), birds and many 

 mammals (Monotremes, 

 Marsupials, Walrus, etc.) 

 has atrophied in man 

 and apes, simultaneously 

 with the disappearance of 

 a retractor muscle, but 

 exists in a rudimentary 

 form in the lower races of 

 mankind. 3 



Schlampp 3 has found 

 FIG. 87. Diagrammatic section of the right . , . . . . 



eye. (Thome, Zoologie.) o, Optic minute histological varia- 



nerve; Fc, Fovea centralis, or macula t j ons j n t he Structure of 



lutea ; S, Sclerotic ; Ch, Choroid ; R, 



Retina; Cv, Vitreous humour; Os, Ora the granules 111 the plg- 



serrata ; Cc Ciliary bodies; Cj, Con- ment j of the retma 



junctiva ; C, Cornea ; J , Ins ; L, Lens ; *, 



Anterior chamber; **, Posterior cham- In man theyarespilldle- 



ber, both containing aqueous humour. shaped cylinders 



In porpoises they are short, round rods, cut off obliquely at 

 each end. 



In doves they are long, narrow and ribbon like. 



In frogs they are biconical. 



In pike they are truncated, stumpy rods. 



The shape of the pupil is very variable. 



In man, apes and dogs, it is round. 



1 Schlampp in Ellenberger's Histologie, p. 639. 



2 Wiedersheim, loc. cit., pp. 160-62. 

 3 Schlampp, loc, cit., p. 639. 



