LIST OF ILLUSTRATIONS. XXI 



PIG. PAGE 



193. Indistinct image, from deficient refraction . . . 615 



194. Rods and cones, of human retina . . . (Schultze) 618 



195. Surface of the retina, showing ends of rods and cones (Helmholtz) 619 



196. Diagram, for showing blind spot of the retina . . (Helmholtz) 621 



197. Section of the retina, through macula lutea and fovea . (Schultze) 624 



198. Section of the eyeball, showing direct and indirect vision . . 629 



199. Catoptric images in the eye .... (Helmholtz) 632 



200. Change of position in catoptric images during accommodation 



(Helmholtz) 633 



201. Vision for distant objects . . . . . .633 



202. Yision for near objects ....... 633 



203. Emmetropic eye, in vision at long distances . . (Wundt) 636 



204. Myopic eye, in vision at long distances . . (Wundt) 636 



205. Single and double vision, at different distances . . . 639 



206. Skull, as seen by the left eye . . . . . .641 



207. Skull, as seen by the right eye ...... 641 



208. Eood's apparatus, for measuring duration of electric spark . . 644 



209. Ossicles of the human ear .... (Rudinger) 650 



210. Ossicles of the ear, in situ .... (Rudinger) 651 



211. Bony labyrinth of the human ear ..... 655 



212. Bony cochlea of the human ear . . . (Cruveilhier) 660 



213. Organ of Corti . . . . . . .662 



214. Cysticercus cellulosae ..... (Davaine) 673 



215. Taenia solium ........ 674 



216. Trichina spiralis ; encysted ...... 675 



217. Infusoria, of various kinds . . (Ehrenberg and Stein) 676 



218. Stylonychia mytilus ; unimpregnated and impregnated (Stein) 679 



219. Cells of Bacterium termo ...... 680 



220. Blossom of Ipomoea purpurea ; showing sexual apparatus . . 682 



221. Single articulation of Taenia crassicollis .... 683 



222. Human ovum ........ 685 



223. Human ovum, ruptured by pressure ..... 686 



224. Female generative organs of frog . . . . 687 



225. Mature frog's eggs ...... . 688 



226. Female generative organs of fowl ..... 690 



227. Diagram of the fowl's egg ...... 691 



228. Uterus and ovaries of the sow .... . 692 



229. Generative organs of the human female .... 693 



230. Spermatozoa ........ 696 



231. Graafian follicle, near the period of rupture .... 707 



232. Ovary with Graafian follicle ruptured ..... 707 



233. Human Graafian follicle, ruptured during menstruation . 714 



234. Corpus luteum of menstruation, three weeks old . . 715 



235. Corpus luteum of menstruation, four weeks old . . . 716 



236. Corpus luteum of menstruation, nine weeks old ... 716 



237. Corpus luteum of pregnancy, two months old . . . . 718 



238. Corpus luteum of pregnancy, four months old . . . . 718 



239. Corpus luteum of pregnancy, at term ..... 719 



240. Segmentation of the vitellus . . . . . . 722 



241. Impregnated egg, with embryonic spot .... 724 



242. Impregnated egg, in an early stage of development . . . 725 



243. Impregnated egg, at a more advanced period .... 725 



