The Limbs 



341 



cryptorchid sexual reflex, a male voice, form and behavior. 

 Such a case was readily castrated by us through the ample 

 vagina in the same manner as spaying a mare. (Fig. 58). The 

 elongated clitoris, which projected 2 or 3 inches beyond the 

 vulva, was amputated. The udder was well developed. In 

 other cases in the horse, we have observed well developed mam- 

 m« with testicles resting just above and to the outer side of 

 them, an abbreviated penis and no vulva. Between these types 

 various gradations appear. In a boar, as shown in Fig. 14, we 

 found a male gland (testicle) on one side and a female, (ovary) 

 on the other. 



The Limbs. 



In a rabbit eml^ryo of about the tenth day, the mesoblastic 

 cells on either side of the notochord become grouped into cuboid- 

 al masses, divided from each other by transverse lines, which 

 are known as somites or primitive segments. The first pair ap- 

 pears in the cervical region prior to the closure of the neural 

 tube and additional somites appear, extending forward toward 

 the head end and backward toward the tail. From these somites 



Fig. 59. Rabbit embryo of the ninth .lay ; seen from the donsal 

 side (after Kolliker.) X^i. . 



stz. Stem zone, pz. Parietal zone. In the stem zone S pairs of 

 somites appear on either side of the chorda dorsahs and nenral 

 tube. 



ap. Area pellucida. rf, Medullary groove, vh, Fore-bram. 



ab. Eye vesicle, mh, ]Mid-brain. hb. Hind-brain. 



uw. Primitive segment, h. Heart. 



ph, Pericardial portion of body cavity. 



vd. Margin of entrance to foregut. af, Amniotic fold. 



Vena omphalo-mesentenca. 



Heisler). 



