PRENATAL GROWTH OF THE PIG 



119 



0.000003 cc, and (assuming the specific gravity as 1) the weight 

 about 0.000003 g. 



Keibel ('97) describes three pig embryos, aged twenty-two days, 

 which varied from 11.7 mm. to 14 mm. in length. In the small- 

 est litter observed by me, the average crown-rump length was 



.35 



.25 



§15 



Q-.05 



39 58 



84 107 . 130 157 



Body Length in Millimeters 



191 



215 



242 



262 



Fig. 4 Curves showing the relative growth of the testes, ovaries, spleen and 

 thymus. These curves were secured by arranging the average percentage (for 

 the litter) which the organs form of the net body weight, according to the aver- 

 age body length (in millimeters). In certain cases, several litters are combined, 

 the average of the litter averages being taken (see above). The broken line at 

 the right shows the trend of the post-natal relations, as indicated by the obser- 

 vations on the adults. The information thus gained is only general, as there 

 are no indications concerning the age of the specimens, or the rapidity ^^-ith 

 which the changes take place. 



13.6 mm., and the average weight 0.25 g. (litter 13, which con- 

 tained eight specimens, only three of which were dissected). 

 These embryos would probably not be more than 23 days old, 

 according to Keibel's figures, although some allowance must be 

 made for variation. 



The duration of pregnancy in the pig is given by Coburn ('94) 

 as 112 days, by Long ('06) as usually 112, varying from 110 to 



