PATHOLOGY OF PREGNANCY AND PARTURITION 429 



With regard to lesions in the external nerves of the eye, 

 nystagmus has a more serious significance. In man it may be 

 the result of myopia, either congenital or acquired in early life ; 

 in this case it leads to no consequences but has very little chance 

 of improvement. 



In animals, such as swine, horses and dogs, it is always the 

 result of poisoning or of cerebral disease, and thus demands a 

 cautious prognosis. Squint, on the other hand, has hardly any 

 significance in animals ; internal strabismus, due to paralysis of 

 the external recti muscles, is commonest in horses, cows and dogs. 



As might be expected, nothing is known of defects of ac- 

 commodation in animals. With regard to refraction, Matthies- 

 sen, Berlin and others have shown that a slight grade of hyper- 

 metropia is present in most domestic animals ; Berlin estimates 

 it in horses as from one to two diopters, though higher degrees 

 may of course occur. A frequent cause of squint in horses is 

 astigmatism, that is to say, an inequality of the dioptric apparatus 

 in its different diameters; according to Moller, it is usually 

 present in horses and other domestic animals. 



4. Pathology of Pregnancy and Parturition. 

 (a) Diseases of Pregnancy. 



Pregnancy in the human being may be unfavourably in- 

 fluenced by abnormal conditions of the uterus which in other 

 mammals are either non-existent or else approximate to the 

 normal. Thus, a uterus unicornis in the human species may 

 have its single horn so much stretched by the growth of the 

 foetus that the wall is thinned and eventually ruptured. The 

 same thing may take place in the uterus bicornis when a foetus 

 develops in one-half. 



In most carnivora and edentata, and in some rodents, the 

 uterus is divided into two parts by an incomplete septum, and 

 the young lie to the right and left. A human uterus bilocularis, 

 with a septum arising from the fundus, causes a cross position 

 of the foetus like the uterus bicornis, which is the normal form 

 of uterus in ruminants, pachyderms and ungulates, and in them 

 gives rise to no difficulties during pregnancy. 



Acute retroversion due to external forces, or one which is 



