438 Veterinary Obstetrics 



it from other lesions. The spinal column of the horse forms an 

 arch from the first dorsal vertebra to the sacrum. This arch is 

 chiefly maintained by the linea alba, originating from the sternum 

 in front and ending behind on the pubis, as the prepubian tendon, 

 thus acting as a powerful tie. If the prepubian fendon parts at 

 the abdominal rings, the arch of the spine can be no longer com- 

 pletely maintained and the back drops downwards, as is shown 

 at C in Fig. 82, producing lordosis, or " sway back," while the 

 pubis becomes displaced backwards. This causes the external 

 ilial tuberosity to descend and the ischial tuberosity to become 

 displaced upwards, decreasing the slant of the hip, as we have 

 intimated at B in Fig. 82, in contrast to the normal slant at A. 



The rupture of the tissues between the abdominal rings oblit- 

 erates these and relaxes the fixation of the mammae in them. 

 The abdominal tunic also becomes ruptured on the same level, 

 the skin becomes greatly stretched, the milk glands are displaced 

 downwards and forwards, as indicated by the position of the teat 

 atT in Figs. 82, 83, 84 and 85, and the glands become less con- 

 spicuous because of the compression from the stretching of their 

 capsule derived from the ruptured abdominal tunic. 



In Figs. 82-84, the displacement is comparatively mild. In 

 some cases it is much greater, as shown in Fig. 85, from St. Cyr. 

 No other form of rupture could cause such displacement of the 

 mammary gland, as it is firmly fixed to the abdominal ring so 

 long as that remains intact. 



The umbilicus is also necessarily displaced forwards and down- 

 wards, as shown at U in Figs. 83 and 84. The rupture having, 

 involved the entire prepubian tendon, and the abdominal tunic 

 having given way, the rent may extend on either side outwardly 

 from the external side of the abdominal ring until it includes the 

 entire abdominal floor. Through this great rent, the gravid 

 uterus and other viscera drop down upon the skin and skin 

 muscles and, pu.shing the abdominal tunic and musculo-tendihous 

 portions of the abdominal floor forwards, bear the skin and skin 

 muscle downward until the hernial sac may reach the tarsus or 

 even lower. Early in the progress of the lesion, firm upward 

 pressure with the hand, in the premammary region, discloses a 

 tense hernial touch without a distinct boundary. As the rupture 

 progresses, the hernial touch becomes more pronounced. 



The downward displacement of the abdominal viscera, with 



