QUESTIONS AND ANSWERS 273 



Describe the operation of artificial impregnation. 



This operation consists of transferring semen from the vagina 

 of a female, with which the male has recently copulated, to the vagina 

 of another female. No special apparatus is necessary, in fact, any 

 ordinary sterile syringe, or the hand will answer the purpose. 



Cleanliness must be observed. Allow the male to serve a female 

 and, promptly afterward, withdraw some of the semen into the 

 syringe and inject it into the cervical canal of the second female. 



Describe an impregnator and state how impregnation is accomplished 

 by its use. 

 An impregnator is an instrument designed to keep open the os 

 uteri during copulation and thus insure a direct discharge of the 

 semen into the uterus. It consists of a hollow, soft-rubber tube, 

 3 to 4 inches in length. It is constricted in the middle portion and 

 flanged at the postef-ior end to prevent it from falling into the 

 uterus. Those who advocate its use do so with the belief that sterility 

 in most cases is due to occlusion of the os. Intelligent breeders 

 ignore the instrument. Prof. Williams, in his "Veterinary Ob- 

 stetrics," regards the use of impregnators as "a harmless diversion 

 which ordinarily will not prevent conception." 



Mention the changes in position of the neighboring organs during the 

 development of the uterus in pregnancy. 

 The vagina is drawn forward except in the last stages of gesta- 

 tion, when the foetus protrudes into the pelvic cavity. The stomach 

 is pushed to the left and the intestines and liver are compressed; 

 the diaphragm is pushed forward and the abdomen becomes en- 

 larged, rounded and pendulent. 



State the function of the liver in fetal life. 



It serves as a blood-forming and blood-purifying organ. 



What is the blastoderm ? How are its membranes divided ? 



The blastoderm is the delicate membrane which lines the zona 

 pellucida of the impregnated ovum. Its membranes are divided into 

 hypoblast, mesoblast and epiblast. 



What do the different layers of the blastoderm form? 



The hypoblast forms the epithelium of the alimentary canal and 

 of the organs connected with it, and that of the air-passages. 



The mesoblast develops into the skin and connective-tissue struc- 

 tures, the bones, muscles, organs of excretion, and internal genitals. 



From the epiblast are developed the epidermis and epidermic 

 tissues, such as nails, hair and glands of the skin, the nervous sys- 

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