454 



GENERATION. 



With regard now to the time at which the 

 ovum first enters the uterus in the human fe- 

 male, let us examine the facts which are 

 before us. The greater number of observations 

 of this kind are made on aborted products; 

 many of these are malformed or diseased, in 

 consequence of which very probably they have 

 been thrown off by abortion ; others are injured 

 by the violence of the action which causes the 

 uterus to be emptied of its contents. Our 

 knowledge of the time of conception is generally 

 founded upon the cessation of the menstrual 

 flow on the first occasion when it ought to 

 have recurred after conception has taken place, 

 and conception may in the greater number of 

 instances have taken place at any period of the 

 interval. In a very few cases only have we 

 any means of determining the time of concep- 

 tion, and in still fewer instances has there been 

 an opportunity of examining the uterus in situ 

 at an early period after conception when the 

 period of sexual intercourse was known. In 

 by far the greater number of instances, there- 

 fore, there may be an error in the calculation of 

 ten days or a fortnight. 



It is by no means rare to see specimens of 

 the human ovum or foetus in anatomical col- 

 lections marked as being a fortnight or three or 

 four weeks old ; but it is now generally ac- 

 knowledged that the greater number of these 

 are incorrectly marked. We have seen, however, 

 more than one such ovum, which, both from 

 the history of the cases and from the structure 

 and size of the parts of the ovum and fcetus, 

 we should be inclined to consider as dating 

 between three and four weeks after concep- 

 tion.* 



once burst it is impossible to recognize any parts 

 of the ovum, frequently in instances where we 

 are certain it has existed. Baer in a second 

 epistle (published in Breschet's Repertoire, vol. 

 viii. p. 175) mentions these difficulties of mani- 

 pulation in extracting the ova from the gravid 

 uterus of the dog during the early periods, and 

 advises that, on account of the violent contrac- 

 tions which are apt to ensue in the uterus from 

 its exposure to the air, the animals should not 

 be opened, but left perfectly quiet for eight or 

 twelve hours or more after death. We have fre- 

 quently pursued this plan advantageously in the 

 rabbit and cat ; and have even found it neces- 

 sary to harden the ovum and uterus in alcohol 

 before being able to extract the former. The same 

 circumstances may account for our never finding the 

 ovum of the sheep before the seventeenth day, for 

 those we examined were all killed at the market, 

 and consequently opened immediately after death 

 while the contractility still remained in the uterus. 

 At earlier periods we have in fact frequently found 

 shreds of membrane, and some of the earliest ova 

 which we found were partly destroyed ; but in a 

 very short time afterwards the membranes of the 

 egg and parts of the fo?,tus acquire sufficient con- 

 sistence to resist the pressure. 



* So common in museums are the specimens of 

 blighted ova which are considered as examples of 

 very early date, that the author confines himself 

 here to the mention of those which he has himself 

 seen, making this general remark, that in all those 

 specimens below the alleged age of six or seven 

 weeks, in which the fo?tus and membranes, parti- 

 cularly the amnion, are disproportionate in size, 

 that is, the first very small and the latter large, 



Tbere are some who describe the human 

 foetus at less than a fortnight old, and even as 

 early as the eighth day, as in the well-known 

 and often-quoted example described by Sir E. 

 Home. But there is some reason to think that 

 Sir E. Home was mistaken in the case alluded 

 to. Either, supposing that conception had 

 occurred eight days before death, the body 

 in question was not the foetus, or if it was the 

 foetus, it must have been considerably older 

 than he supposed. 



The earliest example of the human ovum 

 with which we are acquainted is that mentioned 

 by M. Velpeau in his work sur I'Embryologie 

 Hum aine ; which, if he was not deceived by 

 the person who gave it to him, he had the best 

 reason to believe was discharged on the four- 

 teenth day after sexual intercourse. 



This ovum, the description and drawings of 

 which are very meagre, is described as about 

 the size of a pea ; the fcetus was already some- 

 what formed, though very small ; and all points 

 of structure in the foetus and ovum appear to 

 us (so far as we can judge from the description) 

 to correspond with one another, and to shew 

 that the product was quite natural. This ovum 

 from its size and from the state of advancement 

 of the fcetus must have been in the uterus at 

 least two or three days. 



We possess also the recent record of two 

 valuable observations made on the structure of 

 the gravid uterus of females dying suddenly 

 eight days after sexual intercourse ; the one by 

 Weber, the other by Professor Baer. No ovum 

 was detected in either of these instances either 

 in the uterus or tubes. We feel inclined to 

 place much reliance on these two observations 

 as being made by persons well acquainted with 

 the various circumstances necessary to be at- 

 tended to in such a delicate investigation, and 

 with all the advantages of recent knowledge, 

 and though they afford negative evidence only, 

 yet we are disposed to found upon them as 

 proofs that at the eighth day the ovum has not 

 descended into the uterus. 



On comparing the degree of advancement 

 of the foetus in the ovum described by Velpeau 

 and in others with that of the fcetus in the dog, 

 cat, and sheep, at known periods, we would 

 hazard the opinion that the human ovum arrives 

 in the uterus on the eleventh or twelfth day after 

 conception. Valentin thinks the twelfth or four- 

 teenth day, but we are inclined to believe that 

 it cannot be much later than in the dog. 



Change of the uterus after conception. 

 Before the arrival of the ovum in the uterus, 

 a change has already taken place in the interior 

 of that organ preparatory to the reception of 

 the foetus. An exudation of a substance having 

 many of the characters of organizable lymph 



then the product is unnatural, and we ought to 

 judge of its age more by the extent of the mem- 

 branes than by the size of the foetus. We feel 

 inclined to believe that some of the views adopted 

 by Dr. Pockels of Brunswick, in his interesting 

 paper on the early structure of the human ovum 

 and fcetus (to the consideration of which we shall 

 return in the. article OVUM), are founded upon the 

 examination of unnatural specimens. 



