DEVELOPMENT OF THE F(ETUS. 563 



glands, kili-cyc, r.nd suprarenal capsules are present. At 10 

 ^-eeks, the embryo measures Sf inches; the internal and 

 external genital or£;an2 are formed. At 11 weeks, the embryo 

 measures 4^- inches. At 12 weeks, 4f inches; ,and at 13 weeks 

 5|- inches. 



(b.) Ox. — At 9 wseks^ the embryo measures almost 3 J inches. 

 At 10 weeks, S|- inches. At 11 weeks, 4f inches, and its 

 development corresponds to that of the horse's embryo of the 

 same ags ; mouth-groove and nostrils are .closed by a thin mem- 

 brane ; the divisions^ of the stomach are present. At 1 2 weeks, 

 the embryo measures' 5|- inches. 



(c.) Sheep and Goat. — At 8 weeks, the length of the embryo 

 is about 2 inches. At 9. weeks, 3f inches ; the nostrils are still 

 closed. 



(d.) Pig. — Length of embryo in the 8th week is 3^ inches. 



(e.) Carnivora. — Length of embryo in the 5th week is 2^ 

 inches. 



V. Period. — Includes, in the horse, the 14!th to the 22iid 

 week; in, the ox, the 13th to the 20th ; in the sheep and goat, 

 the 10th to the 13th; in the pig, the last half of the 8th, the 

 (Hh, and the 10th week; in carnivora, the 6th week. 



(a.) Horse. — During this period the embryp increases from 5-| 

 inches to 14|^ inches. At 17 weeks, the first hair appears on 

 the lips. At 22 weeks, the lips, eyelidS; and point of tail are 

 provided with hair. 



(b.) Ox. — The embryo increases from 5^ inches to 12f. At 

 18 weeks, the hair appears, and the testicles descend into the 

 scrotum. 



(c.) Sheep and Goat. — At the end of this period the 'embryo 

 measured 6|^ inches ; hair is still wanting. 



(d.) Pig. — The embryo measures 5^ inches. 



(e.) Carnivora. — The embryo has a length of 3^ inches. 



VI. Period. — Includes, in the horse, the 23rd to the 34th 

 ^veek; in cattle, the 21st to the 3 2nd week ; in the sheep and 

 ^oat, from the last half of the lj3th to the 18th week; in the 

 pig, from the 11th to the first half of the 15th ; in the dog, the 

 7th and 8th weeks ; in the cat, to the end of the 7th week. 



(a.) Horse. — The embryo grows about one inch weekly, and 

 -at the end of the period has a length of about 27 inches. The 



