THE SEXUAL ORGANS. 653 



conclusion, in the first place, can be drawn from Remak's statement 

 (1. c.), that the nerves, at the time of pregnancy, enlarge and acquire a 

 gray color, a change depending upon an increase of nucleated fibres, 

 because no grounds exist upon which it can be decided whether these 

 nucleated fibres are embryonic nerve-fibres, or a form of connective 

 tissue. On the other hand, we are indebted to Kilian for careful re- 

 searches in animals, which prove with certainty that the uterine nerves, 

 at the time of pregnancy, may be traced further into the substance of the 

 uterus, in the form of dark-bordered fibres ; whilst at an earlier period, 

 in part even before they enter the uterus, in part when they have scarcely 

 reached it, they possess the nature of embryonic non-medullated fibres. 

 For this reason, Kilian succeeded also in tracing the nerves in the gravid 

 uterus much further into the parenchyma than at other times. He perceived 

 no evidence of a formation of new nerve-fibres in the trunks, and regards 

 such an occurrence as improbable ; for otherwise a new formation of 

 ganglionic substance must also be assumed, which is unlikely. Some- 

 thing of the kind appears to me by no means impossible, because the 

 multiplication of the ganglion-cells and of the fibres would only take 

 place once in the first pregnancy ; it is also conceivable that newly 

 formed nerve-fibres are added to the others simply as branches, and 

 consequently it will be more prudent to wait and see upon which side 

 Remak's statements, with respect to the human subject, incline. Upon 

 this, however, I would also remark, that a thickening of the nerves may 

 undoubtedly be produced by an increased size of the already existing 

 fibres and an augmentation of the neurilemma, and that the nerves, by 

 a multiplication of their ultimate divisions, are fully enabled to ramify 

 over larger spaces than at other times. 



The increased size of the vessels, both of the arteries, and, above all, 

 of the veins, at the time of pregnancy, is very considerable ; owing to 

 which, at this period, the middle layer of the muscular substance, con- 

 taining the larger vessels, is much more distinct from the other two. 

 The alteration which takes place in the vessels of the mucous membrane, 

 at the point where the placenta is formed, cannot here be entered upon ; 

 and I will only remark that I agree with those who believe that large 

 vascular trunks exist in the human uterine placenta, at the border and 

 on the convex surface, whilst in the interior there are only lacunce with- 

 out walls, between the villi of the chorion (vide Kiwisch, " Geburtskunde," 

 I. p. 151, et seq. ; C. Wild, "Zur Physiologie d. Placenta," Wurzb., 

 1849; Virchow, " Archiv," III. p. 449; Schroder v. d. Kolk, in the 

 "Verb. d. Nied. Instituts," 1851). In the rest of the decidua, the 

 capillaries are frequently excessively enlarged ; according to Virchow 

 ("Archiv. f. path. Anat.," III. p. 436), its superficial capillaries, in the 

 sixth week of pregnancy, reach the size of 0-027-0-045 of a line, and 

 become extremely thin-walled, as are, probably, also those in the part 



