SECT. 206.] MENSTRUATION AND PREGNANCY. 46 1 



body; this enlargement especially affects the superficial network, 

 on which account the raucous membrane appears of a bright red 

 ('(Hour. With the effusion of the blood consequent on the rupture 

 of the superficial capillaries, the epithelial lining of the body and 

 fundus is for the most part also thrown off., and its cells are always 

 found in large quantities, mixed with the blood and mucus which 

 till the cavity of the uterus; on the other hand, we are not to re- 

 gard as a normal process the detachment of the mucous membrane, 

 as a whole or in fragments, which sometimes occurs after or during 

 the catamenia. After the menses, the parts quickly return to their 

 previous condition, and the epithelium is formed anew. 



Of an entirely different character are the changes which are 

 produced in the uterus by pregnancy; among these, however, in a 

 microscopical point of view, only the increase of the organ is of 

 interest. This enlargement, as is well known, depends upon an 

 enormous increase in the circumference and in the cavity of the 

 organ, and upon an increase in substance amounting on an average 

 (J. F. Meckel) to twenty-four times the original bulk; the thick- 

 ness of the walls is at first increased, but it afterwards diminishes, 

 usually from the fifth month of pregnancy onwards. The chief seat 

 of the changes by which the increase in volume is effected, is in 

 the muscular substance of the uterus. Here there are two processes 

 which operate together to effect this increase ; first an enlarge- 

 ment of the muscular elements already existing, and secondly, a 

 new formation of similar elements. The former method is so 

 considerable, that the contractile fibre-cells, instead of being 

 o - 02'" to 003" in length, and 0'002"' in breadth, as at other 

 times, measure at the fifth month of pregnancy, o - o6'" to 0"i2" 

 in length, 0'0025'" to o - oo6'", or even O'oi"' in breadth : in the 

 latter half of the sixth month, they measure O'i" to 0*25"' in 

 length, 0-004'" t° o*oo6"' in breadth, o , oo2'" to o*oo28'" in thick- 

 ness; so that they increase between seven and eleven times in 

 length, and between two and five times in breadth. The new 

 formation of muscular fibres is especially to be observed at the 

 beginning of pregnancy in the innermost layers of the muscular 

 coat, where newly formed round cells, o*oi"' to 0*018'" in di- 

 ameter, are found in large quantities and in all states of transition 

 into fibre-cells of 0-02'" to o , o3'" in length ; this process, how- 

 ever, is not absent even in the outer layers. From the sixth 

 month onwards, the mode of development of muscular fibres 

 appears to cease; at least, in the twenty-sixth week I have found 

 nothing but colossal fibre-cells in the whole uterus, and no trace 



