80 NON-SPECIFIC OR GENERAL DISEASES 



that form the framework of the pelvis completely enclose the 

 entrance to it. It is only in the young mother that the pelvic 

 bones give way slightly to the pressure on them by the foetus. 

 It can be readily understood, that when the young is large in 

 proportion to the diameter of the pelvic inlet, it is difficult 

 for it to pass through. This occurs when mothers belonging 

 to a small breed, are impregnated by a sire belonging to a large 

 breed of animals. It may also occur if tlie mother is fed too 

 fattening a ration and not permitted sufficient exercise. 



The part of the fcrtus that presents itself for entrance into 

 the pelvic cavity and its position are of the greatest impor- 

 tance in giving birth to the young. Either end of the foetus, 

 or its middle portion may be presented for entrance. The 

 anterior and posterior presentations may be modified by the 

 position that the foetus assumes. It may be in a position that 

 places tlie back or vertebrse opposite the upper j)ortion of the 

 inlet, or the floor or sides of the pelvic cavity. These posi- 

 tions may be modified by the position of one or both limbs, or the 

 head and neck being directed forwards instead of backwards. 

 In the transverse presentations, the back, or the feet and abdo- 

 men of the fo-tus may present themselves for entrance to the 

 pelvic cavity. These presentations may show three j)ositions 

 each. The head may be opposite the upper walls of the inlet, 

 the foetus assuming a dog-sitting position, or it may lie on either 

 side. 



In order to overcome the friction between the foetus and the 

 wall of the maternal passages, these parts are lubricated by the 

 fluids that escape from the " water bags." If birth is prolonged 

 and the passages become dry, birth is retarded. The hair offers 

 some resistance in a posterior presentation. Young mares that 

 become hysterical have abnormal labor pains that seem to hold 

 the foetus in the womb instead of expelling it. 



Care of the Mother and Young. — Although birth is gener- 

 ally easy in the different domestic animals, it may be difficult 



