Anatomical Changes. Pathogenesis. 161 



the foals of affected mares are infected at tlie time of birth 

 (Tatray, Sohnle). 



The possibility that the infection may also occur from the 

 external genital organs cannot be excluded. The contagion 

 which may enter the mucous membrane of the uterus might 

 localize there and later enter the vascular system of the devel- 

 oping placenta, and in this manner also the body of the foetus. 

 In this way it may be explained that some animals give birth 

 for several consecutive years, to affected offspring, a condition 

 not infrequently observed, especially in thoroughbred mares. 

 In case of an intrauterine infection the infective agent remains 

 lodged only in the finer blood vessels of the internal organs 

 and causes at these places alone inflammatory processes, while 

 the umbilical vessels remain intact (Peiffer found only 37% of 

 affected foals with umbilical vessels diseased). 



The infection probably does not occur through the digestive 

 and air passages; at least up to the present time the disease 

 could not be produced artificially in this way in calves (Nocard)-. 



The greater or lesser frequency with which the disease 

 occurs can in various localities be referred to existing local con- 

 ditions. The fact that the disease is only rarely observed among 

 common bred stock which is kept out of doors most of the time, 

 as well as in stables with only few animals can be readily 

 explained by the fact that under such conditions the animals 

 are not confined in close quarters and therefore there is less 

 chance for infection. 



Since the infective agents, the bipolar bacterium, as well 

 as the colon bacillus, can propogate in the soil, the disease may 

 appear without introduction from outside, as a result of direct 

 infection from the soil; nevertheless it is most frequently the 

 result of an introduction from adjoining farms, while if the 

 disease has already been introduced in certain premises it is 

 propagated by the secretions an^ excrements from the infected 

 animals. 



Formerly breeders attributed great importance to heredity 

 in the appearance of pyosepticemia. However except for the 

 cases of intrauterine infection, in which the infection of the 

 foetus is directly associated with the infection of the mother, 

 the disease occurs only when the conditions for the infection 

 of the sucklings are favorable. 



Pathogenesis. The bacilli which enter the umbilical veins 

 commence to multiply in the coagulated blood of these vessels, 

 on the one hand cause the thrombus to break down, and on the 

 other hand produce an inflammation of the intima and probably 

 also of the external layer of the walls of the vessels. The 

 breaking down of the thrombus progresses gradually inward 

 until it reaches the end, when the infection may come in contact 

 with the liquid blood contained in the same vessel, or m the 

 portal vein, coming in direct contact with the circulatmg blood. 

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