650 



SPECIAL HISTOLOGY. 



Fig. 268. 



creased bulk of the organ only, is of interest. This enlargement, as 

 is well known, depends upon the great augmentation of 

 the circumference and of the cavity ; at first with in- 

 creased, and afterwards (usually from the fifth month 

 onwards) with a diminished thickness of the walls, and 

 an increase in bulk, amounting on the average to twenty- 

 four times the original size ( J. F. Meckel, "Anat.," IV. 

 691). The mode in which this change is brought about 

 was, as regards the histological conditions, until a recent 

 period, it may be said, entirely unknown ; but, in the 

 main point, is now sufficiently made out. The principal 

 changes occur in the muscular coat, to which the in- 

 creased volume of the uterus is chiefly to be assigned, 

 and there are two processes which participate in 

 common in its production : in the first place, an en- 

 largement of the pre-existing elements ; and secondly, 

 a new formation of them. The former is so conside- 

 rable, that the contractile fibre-cells, 

 instead of a length of 0-002-0-003 

 of a line, and width of 0-002 of a 

 line, as elsewhere, in the fifth month 

 present a length of 0-06-0-12, and 

 width of 0-0025-0-006, or even 0-01 

 of a line, and in the second half of 

 the sixth month, a length of 0-1- 

 0-25, a width of 0-004-0-006, and 

 a thickness of 0-002-0-0028 of a 

 line; consequently, their length is 

 increased from seven to eleven times, 

 and their width from twice to five 

 times. The new formation of mus- 

 cles may be observed in the first half 

 of pregnancy, especially in the in- 

 nermost layers of the muscular coat, 

 where newly originating cells, 0*01- 

 0-018 of a line in size, in all stages 

 of transition into fibre-cells of 0-02 

 -0-03 of a line, always occur in great 

 quantity ; but it takes place also in 



FIG. 268. a, muscular fibre-cell from a gra- 

 vid uterus, at the sixth month ; 6, its middle 

 portion, after treatment with acetic acid, and 

 exhibiting the appearance of a membrane ; c, nucleus of the fibre-cell. Magnified 350 

 diameters. 

 FIG. 269. A uterine gland from a woman in the first pregnancy, eight days after conception. 



