OE THE INTESTINES. 149 



carnivorous animals. Why there should be this difference in the first 

 [small intestines] is not so easily accounted for ; but perhaps the last 

 [difference] is to allow of a longer continuance of absorption, as the 

 food is less similar [to the animal it is to become part of] in the herbi- 

 vorous than in the carnivorous [species] ; and therefore it has a less 

 tendency to putrefaction, as we find to be the case ; for in all herbivorous 

 animals we have their excrements less putrid than in the carnivorous 

 ones. Those animals that have but a short caecum or none, and which 

 generally have but a short and small colon, have their excrements always 

 thin. 



What is the use of the villous coat of the intestine ? It cannot be 

 for absorption, as many of the surfaces of cavities that absorb copiously 

 are entirely smooth. Is it for sensation ? 



In many animals it was necessary to have the last part of the intes- 

 tines [colon is meant] larger than the others, that the food might be 

 deprived of its thinner parts ; and, perhaps, the lymphatics are not so 

 large here as in other parts. The colon is largest hi those animals 

 whose food has the least nourishment in it; which food does not go 

 wholly through the stomachic process [is not completely digested in the 

 stomach], and which food undergoes but little change, consequently 

 such animals, e. g. the horse, &c, have a much larger quantity of ex- 

 crements : therefore the contents must stay longer [in the colon] than 

 in the other intestines. 



However this may be, it is certain that the faeces have not such a 

 quick passage, therefore must become putrid ; which was the cause 

 perhaps of a valve at the termination of the ileum, that these putrid 

 contents might not regurgitate. If we understand the use of a valve, 

 we shall understand the use of a caecum. This seems to be no more 

 than the valvular insertion of the ileum * ; for if it had been a sudden 

 swell in the gut, there could have been no valve. The caecum is longer 

 in some animals than in others. In all animals that I know, the length 

 is in proportion to the width, except in the human subject, where it is 

 shorter ; and in man it is more fixed, which may be one reason of its 

 proportions. 



A new-born child has no air in its stomach or guts ; of which one 

 reason is, that they do not take down anything by the mouth ; nor 

 is there any putrefaction, or anything analogous to it in the guts. 



In the human subject there is a difference between the intestines 

 of the foetus and the adult. In the foetus there are no ' valvules con- 

 niventes;' but the intestines are longer ha proportion. Thus in 



1 [Hunt. Prep. No. 724.] 



