650 



SPECIAL HISTOLOGY. 



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 sufiiciently made out. The principal 

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

 creased volume of the utci'us 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 2)7'e-cx{sting 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. 2G8. — 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. 



a I 



