CHAP. XLTII.] OF THE PLACENTA. 615 



towards the end of the second month ; and by the third it assumes 

 its ordinary character. As the uterine vessels become enlarged, 



Fig. 290. 



Villi of the foetal portion of a placenta. After E. H. Weber. 1. Artery. 2. Vein. Mag- 

 nified 100 diameters. 



the rush of blood through them is accompanied with a well-known 

 murmur, termed the placental bruit, which is usually detected 

 about the third month. It -is one of the most important signs of 

 pregnancy, and is not liable to be mistaken for the sounds of the 

 foetal heart, because it is exactly synchronous with the mother's 

 pulse, and its situation does not vary. 



Towards the termination of the period of pregnancy, the pla- 

 centa becomes hard, and a curious change takes place in its 

 capillary vessels, which has' only been carefully investigated within 

 the last few years. The alteration consists in the appearance of a 

 number of oil-globules in the coats of the vessels in fact, in the 

 occurrence of fatty degeneration of the foetal tufts. In a former 

 page, we described a similar change taking place in muscular fibre- 

 cells of the uterus, when the period of their activity was passed, 

 and the organ was gradually returning to its former volume. The 

 change alluded to has been looked upon by many pathologists as 

 of a morbid nature, and has been brought forward as one of the 

 causes of abortion ; but the observations of our friend, Dr. Druitt,* 

 and others, show that fatty degeneration of the vessels occurs in 

 * Medico-Chir. Trans., vol. xxxvi. 



