450 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



intervenes between the internal membrane of the villus and 

 the vessels, and gives to this part of the organ a mottled 

 appearance. 



II. OF THE VILLI OF THE CHORION. 



Without entering at present into the question as to the 

 manner in which the villi of the chorion take their origin, 1 

 may state, that as soon as they are distinctly formed, they 

 present a structure which has to a certain extent been repre- 

 sented and described by Easpail,* Seiler,t and others. 



The substance of the tufts consists of nucleated cells. 

 These cells are of different sizes. The smaller are situated, 

 some in the interior, others in the spaces between the latter. 

 The cavities of the larger cells are full of a granular fluid. 

 The surface of the tufts is bounded by a fine but very distinct 

 membrane, which, when minutely examined, is seen to consist 

 of flattened cells united by their edges. 



The free extremity of each villus of the tuft is bulbous. 

 The cells which constitute this swelling are arranged round a 

 central spot. They are transparent and refractive, apparently 

 from not containing the same granular matter as the cells of 

 the rest of the villus and tuft. However short a villus may 

 be, it invariably presents a bulbous extremity, with the 

 peculiar cellular arrangement already described. Here and 

 there, on the sides of the stems of the tufts, swellings of a 

 similar structure may be seen. Each of these swellings is 

 the commencement of a new villus or stem, which, as it 

 elongates, carries forward on its extremity the swelling from 

 which it arose. 



These groups of cells in the bulbous extremities of the 

 villi of the chorion, and in the swellings on the sides of their 



* Raspail. Chemie Organiqm. 



t Seller. Gebarmuiter und das Ei des Menschen in den ersten Schivanger- 

 schaftsmonaten. 



