60 BOVINE OBSTETRICS 



Many observations corroborate these theories ; for in- 

 stance, the occurrence of an abortion just at a time when 

 in the unimpregnated state oestrum would set in ; the expul- 

 sion of a so-called calf mummy daring the period of oestrum. 



Franck found, on conducting a post mortem of cows which 

 died during or after parturition, one or more matured Graafian 

 vesicles almost ready to rupture in the ovary devoid of the 

 corpus luteum. This led him to the deduction that the ovary 

 which did not furnish the impregnated ovum might create 

 reflectorily a genital hyperemia by the pressure of the swollen 

 vesicles upon the sensory nerves, same as during oestrum. 

 According to Ellenberger, the act of birth, the changes which 

 the gravid uterus undergoes, as well as the periodical expul- 

 sive contractions following fecundation, are simply hereditary. 



1. — Labor Pains — Dolores. 



Generally speaking, the words " labor pains " represent 

 the expulsive forces; in a more concrete sense, the uterine 

 contractions. The contractions begin in the muscles of the 

 broad ligaments, next contracts the uterus, and in the further 

 course of parturition the muscular elements of the vagina and 

 vestibule participate. These contractions are periodical; they 

 occur now and then, with definite intermissions. 



Various causes induce uterine contractions. The uterus 

 may contract as the result of irritations originating in the 

 cerebellum, medulla oblongata and spina] cord (Spiegelberg, 

 Frankenhauser, Korner, Obernier); but the uterus itself 

 harbors nerve centres, stimulation of which produces con- 

 tractions. Sensibility is conducted via the spinal nerves. 

 We already stated that advanced pregnancy means a hyper- 

 sssthetic state of the uterus. Excitability of the uterus also 

 increases with rise of temperature and hyperemia of this 

 organ. We further know that dyspnoic blood that is, blood 

 laden with carbon dioxide and wanting in oxygen -is exciting 

 to the uterus. In all probability the stimulus Leading to 

 contraction arises in the uterine nerve centres. Mechanical 



