VI CONTENTS 



I'AUK 



b. Transparent media of the eye . . . . . . . . . . 17 



Vitreous humour . . . . . . . . . . . . . . 17 



c. The retina its structure .. .. .. .. .. .. 17 



The retina, formation of images on . . . . . . . . 20 



d. Adaptation of the eye to vision at different distances . . . . . . 20 



Range of distance through which the human eye is capable of vision . . . . 27 



Effect of a transverse pupil in increasing the distance of vision . . ... 27 



e. Action of the retina and of the sensorium in vision . . . . . . 28 



Particulars of a case in which sight was restored to a person with congenital 



cataract .. .. .. .. .. .. .. 28 



/. Complemental colours . . . . . . . . . . . . 29 



g. Relation of non-luminous rays to the eye . . . . . . . . 30 



h. Binocular vision . . . . . . . . . . . . . . 31 



c. Of tlie sense of hearing . . . . . . . . . . . . 32 



a. Movements of the small bones of the ear . . . . . . . . 32 



5. Of Generation. 



A. The unimpregnated ovum . . . . . . . . . . . . 33 



a. Parts composing the ovum . . . . . . . . . . . . 33 



b. Development of the ovum in the ovary . . . . . . . . . . 35 



Order in which its different parts are fonned . . . . . . . . 37 



Changes attending its growth . . . . . . . . . . 33 



B. TJie semen . . . . . . . . . . . . . . 39 



Form and structure of the spermatozoids . . . . . . . . 39 



Their motion, and the influence of reagents upon them . . . . . . 40 



Their development .. .. .. .. .. .. 41 



The question of their independent vitality . . . . . . . . 43 



Their function .. .. .. .. .. .. .. 44 



c. Tlie discharge of ova from the ovaries .. .. .. .. .. 44 



Independently of sexual intercourse . . . . . . . . . . 46 



Nature and import of the corpus luteum . . . . . . . . 50 



Nature and purpose of menstruation . . . . . . . . . . 57 



D. Fecundation . . . . . . . . . . . . . . 59 



In animals . . . . . . . . . . . . . . 59 



In plants . . . . . . . . . . . . . . 60 



6. Of Development 



A. Changes in the ovum previous to the formation of the embryo . . . . 62 

 Changes in the germinal vesicle and germinal spot . . ... . . 62 



tunica granulosa . . . . . . . . . . 64 



Contraction of the yolk. Formation of the chorion . . . . . . 64 



Division and subdivision of the yolk . . . . . . . . . . 65 



a. In the invertebrata. Several varieties of the process . . . . . . 66 



b. In amphibia and fishes . . . . . . . . . . . . 72 



c. In birds and mammalia . . . . . . . . . . . . 74 



Changes in the ovum after the subdivision of the yolk . . . . . . 76 



a. In invertebrata . . . . . . . . . . . . . . 76 



b. In amphibia and fishes ... . . . . . . . . . . 77 



c. In birds and mammalia . . . . . . . . . . . . {JQ 



B. Development of the embryo . . . . . . . , . . . . #3 



a. In mammalia .. ... .. .. ,. .. ,, 33 



