PRENATAL GROWTH OF THE PIG 121 



As the hogs which go to market are usually about ten to twelve 

 months old, the average weight of the full term fetus from such 

 animals would therefore be approximately 826 g. The oldest 

 litter examined in my observations averaged 745 g. These pigs 

 are therefore probably well along in the last month of fetal life. 



During the 23 days immediately succeeding fertilization, the 

 weight thus apparently increases to about 0.25 g., an actual 

 increase of about 83,000 times the weight of the ovum. Even 

 this figure is too small, as a part of the ovum goes to form the 

 membranes, etc. But this gives an idea of the enormously rapid 

 growth rate in the early stages. For the whole ensuing fetal 

 period of 99 days, the fetus increases in actual weight from . 25 g. 

 to 826 g., or about 3300 times the weight at 23 days. That is, 

 in a period about four times as long, the increase is only about 

 one twenty-fifth as great. If the early rate of increase were 

 maintained throughout the fetal period, the newborn animal 

 would weigh about 12 million billion grams! 



The weight at birth, 826 g., represents an increase of over 

 275 million times the weight of the ovum. 



The four adult hogs examined (age about twelve months) 

 averaged about 104.5 kg. in weight. We may safely assume the 

 average young adult weight to be about 100 kg. The increase 

 from a weight at birth of 826 g. to an adult weight of 100 kg. 

 represents an increase of only 121 times. This is certainly an 

 enormous decrease in the relative growth rate, even when com- 

 pared with the last 99 days of prenatal life. The total increase 

 from the weight of the ovum to the weight of the one year adult 

 (sixteen months prenatal and postnatal time) amounts to about 

 thirty-three billion times the weight of the ovum. 



Althou'gh these data are limited in extent, they show such 

 enormous differences for the various periods that we may safely 

 assume the conclusions of Muehlmann ('00), strongly emphasized 

 by Minot ('07) and Jackson ('09), to be true also for the pig; that 

 is, that growth takes place most rapidly in the earliest stages, the 

 rate decreasing, at first rapidly, then more slowly, throughoat 

 prenatal and postnatal life. 



