I'M) LAWSON G. LOWREY 



SUMMARY 



The general conclusions concerning the growth of the pig may- 

 be summarized as follows: 



1 . The weight of the ovum is about . 000003 g. The increase 

 in weight is at least 83,000 times during the first 23 days. At 

 the end of 112 days (full term) the increase is 275 million. The 

 weight of the (young) adult hog is about 333 billion times that 

 of the ovum. Comparative figures given for the human, rabbit, 

 rat and chick show that all these forms agree with the general 

 law that the rate of growth is by far most rapid at the beginning 

 of j:)renatal life, decreasing at first rapidly, then more slowly, 

 throughout prenatal and postnatal life. 



2. The viscera of the pig embryo (including the brain and 

 spinal cord) taken all together have their maximum relative size, 

 about 38 per cent of the whole bodj^ in the earliest stage exam- 

 ined (15 mm.), decreasing to about 16 per cent at birth. In the 

 adult,, they form nearly 8 per cent of the whole body. 



3. The head attains its maximum observed relative size at 

 18 mm. forming nearly 30 per cent of the total, decreasing to 

 about 22 per cent at birth, and about 6 per cent in the adult. 

 It is always relatively smaller than the human head at Corre- 

 sponding stages. 



4. The brain also attains its maximum observed relative size, 

 at about the same time as the head, forming about 9 per cent of 

 the total and about one-third of the head. In later stages it 

 decreases until near full term it forms almost 4 per cent of the 

 total, and about one-sixth of the head. In the adult it forms 

 about 0.087 per cent of the body, and about one-seventieth of 

 the head. The brain of the pig is at all stages relatively much 

 smaller than that of the human. 



5. The spinal cord has its maximum observed relative size 

 1.87 per cent of total body, at 18 mm. (probably larger in ear- 

 lier stages), decreasing at first rapidly, then more slowly, and 

 forming 0.33 per cent of the body at birth. In the adult, the 

 cord forms about 0.04 per cent of the body. 



6. The eyeballs attain their maximum observed relative size 

 at 86 mm., forming 1 . 15 per cent of the body; decreasing to 0.4 



