SIZE OF BRAIN AND SIZE OF BODY. 829 



than that of the ox. The camel also may be included in this class, as 

 being about the same size. Although many camels are larger, still the 

 bulk of the body is not very much greater than that of the horse and 

 ox. Its brain is very similar in size to that of the ox, but smaller 

 than the horse's brain. The brain of the sheep is a good deal larger 

 than that of the goat, although their bodies are similar in size. The 

 sheep and the pig are also animals which we might classify if we do 

 not take extreme sizes, but compare animals similar in age or bulk. 

 We find that the pig's brain is larger than the sheep's, and corresponds 

 in size very nearly to that of the dog. In the cat the size of the brain, 

 in proportion to the body, is much larger than that of the domestic 

 rabbit, although the size of the two animals is very much the same. 



In "these examples given we have not taken into consideration the 

 order to which the animal belongs in the vertebrate series, but only 

 compared similar sized animals, and in all cases we have compared the 

 brains of adult animals. This is a very important point, as it is found 

 that in all animals, including man himself, the size of the brain, in pro- 

 portion to the size of the body, is much greater in young animals than 

 it is in the adult. In some animals the head is found to grow enor- 

 mously in size as the animal reaches adult age, but the brain does not 

 increase to the same extent. There is generally some reason to be 

 found for this in those animals where it takes place. For example, in 

 the ele^jhant the head of the young animal is by no means out of pro- 

 portion to the size of its brain ; but if we bisect the head of an adult 

 animal we find that the brain only occupies a small cavity, and the rest 

 of the skull is composed of plates of bone with air-cells between them. 

 In the young elephant we find none of those plates and air-cells be- 

 tween the outer and inner layers of cranium, but simply the two layers 

 of bone close to one another ; but we will also find that at this stage 

 the young elephant has no large tusks to carry, and its trunk is light, 

 so that its head is comparatively light. The case is, however, quite 

 different in the adult, when there are two large tusks and a large trunk 

 to carry. In order to support this great weight he requires strong 

 muscles. The great increase in the size of his head, therefore, is to 

 afford a requisite extent of surface for the attachment of the muscles. 

 In order to get this, combined with lightness, the skull is composed of 

 those plates and air-spaces mentioned. 



A very interesting question, but one which it is very diflicult to an- 

 swer, is whether the intelligence of the animal corresponds to the size 

 of its brain. It is very diflicult to make comparisons in many animals, 

 as one animal shows his intelligence in one way, and another in an- 

 other way. However, going over some of the animals whose brains 

 we have compared, we may take as an example the horse and the ox. 

 The horse has the larger brain, and he has undoubtedly the greater 

 amount of intelligence. We find that horses can be trained to a great 

 extent, as may be seen daily in a circus, but the ox has never been so 



