28 BOVINE OBSTETRICS 



the various portions of the body. Blood mixtures t;ike place 

 at the following places : 



1. At tbe portal fissure, a confluence of the vena porta 

 and arterial blood of the umbilical veins. 



2. At the end of the ductus Arantii, into the posterior 

 vena cava, and at the end of the hepatic veins, also into the 

 last named. 



3. In the left auricle, a mixing of the pulmonary blood, 

 carried by the posterior vena cava from the right to the left 

 auricle. The blood of the anterior aorta supplying the 

 anterior extremity experiences now no further change. After 

 coursing through the capillaries into the veins, it returns 

 through the anterior vena cava to the right auricle. From 

 here it gains the right ventricle and pulmonary artery. But 

 the greater part flows through Botalli's duct (ductus BotaM) 

 into the posterior aorta. 



The ductus Botalli is a short tube running obliquely from 

 left to right and before to behind, and connects the pulmonary 

 artery with the posterior aorta. A very small amount of 

 the blood reaches the lungs via the pulmonary artery (arteria 

 pfdmonaris), and from here, after circulating through the 

 capillaries, arrives in the left auricle by the left auricle. 



The placenta is the organ of respiration. What the lungs 

 are to the breathing animal the placenta is to the foetus. In 

 the placenta, more than a simple exchange of carbon for 

 oxygen takes place. Iu all probability, nutritive elements 

 pass the placental filter, although apparently during this 

 process a modification in the composition occurs. Between 

 the villi of the foetal and maternal placenta a thin layer of 

 uterine milk is found. One is of the opinion that nutritive 

 elements from the capillaries of the uterine mucosa carried 

 into the epithelium of the maternal placenta are there changed 

 into uterine milk. Bonnet proved that the fat of the uterine 

 milk is no product of degeneration, but the result of infil- 

 tration. 



The uterine milk, or certain of its constituents, under the 

 influence of pressure, are supposed to enter the epithelia of 



