2. The period of quickening. This, too, is not a reliable source of reckoning the period of gestation. Quickening sometimes takes place, doubtless, before it is perceived. It takes place, also, at very variable periods, as I have elsewhere remarked; sometimes as early as the third month, sometimes not until the fifth, or, perhaps, the sixth. The range of quickening may be said to extend over a period of at least sixteen weeks. Thus it will appear that this mode of reckoning is by no means to be depended upon, although it often has been.
3. Peculiar sensations soon after conception. Some persons experience peculiar sensations within a day or two after conception. This is not true of every case, nor does the same individual experience these symptoms at each time of pregnancy. At one time she may have them, and at another time not.
4. Nausea and vomiting. These symptoms are too indefinite to enable us to form any just idea of the time when conception takes place. Some individuals do not experience them at all; some experience them very soon, almost immediately after conception; others not until the lapse of weeks, in some cases, probably months.
5. Coition. In the generality of cases it is impossible to know at what precise period pregnancy has commenced, because it is not known when the effectual coition took place. Now and then, however, such cases do occur; and in such instances, which are, on the whole, very rare, we find that the period of pregnancy varies somewhat as to its length.
Another method of reckoning has been to count from the time of the last menstrual discharge. Dr. Merriman, of London, has published a table of the births of 144 mature children, calculated from the day after the last menstruation was perceivable. According to this table
| 3 | were born in the | 37th | week. |
| 13 | „ | 38th | „ |
| 14 | „ | 39th | „ |
| 83 | „ | 40th | „ |
| 22 | „ | 41st | „ |
| 15 | „ | 42d | „ |
| 10 | „ | 43d | „ |
| 4 | „ | 44th | „ |
Dr. Guy, of London, gives the following cases:
| A case by | Dr. Nixon | 273 or 276 | days |
| „ | Dr. Montgomery | 280 | „ |
| „ | Dr. Forster, of New York | 283 or 285 | „ |
| A case before | Lancaster Assizes | 284 | „ |
| A case by | Dr. Dewees | 286 or 288 | „ |
| „ | Dr. Desormeaux | 290 | „ |
| „ | Dr. Reid | 292 or 293 | „ |
The results of these cases are as follows:
| Average | of the seven cases | 284 or 285 | days. |
| Minimum | „ | 273 or 276 | „ |
| Maximum | „ | 292 or 293 | „ |
| Range | „ | 16, 17, 19, or 20 | „ |
| Excess | above 280 days, | 12 or 13 | days. |
| Excess | above nine calendar months, | 16 or 17 to 19 or 20 | days. |