828 THE POPULAR SCIENCE MONTHLY. 



body of any member of the group, but a much smaller brain in propor- 

 tion to its body than many of the smaller birds. As a class, however, 

 the birds have large brains in proportion to their body, when com- 

 pared to the other vertebrates, and so present a contrast to the rep- 

 tiles, in which, as already stated, the brain is small throughout the 

 whole group. In the next class of vertebrates — the Monotremata — 

 the brain is large in proportion to their body, but it must be taken into 

 account that this group contains very few large animals, being composed 

 almost entirely of small ones. The size of the brain in the echidna, 

 and the ornithorhynchus, both belonging to this group, is especially 

 large in proportion to the small bodies which the animals possess. 

 This is more remarkable when we consider the low position they oc- 

 cupy in the vertebrate series. In this manner we might go on through 

 the whole series of vertebrates, showing how the larger animals have 

 relatively smaller brains, and also the reverse, that the smaller animals 

 have larger brains for their size. 



"We must now consider, however, the relative size of the brain in 

 animals about the same size, as it is only in that way that we can gain 

 information on the subject. Owing to the difficulties which attend the 

 investigation of this subject, comparatively little is accurately known 

 about it. It may be stated generally that the brain of domestic ani- 

 mals is larger than that of wild animals of a corresponding size of body. 

 As an example of this we may take the case of the dog and the wolf. 

 If the brains of those animals are compared, it will be found (if the 

 animals compared are of the same size) that the brain of the dog is the 

 larger. Again, if we compare the brains of a dog, a badger, and a 

 musk-deer about the same size, we find that the brain of the dog is the 

 largest, those of the other two animals being about the same size. It 

 will be observed that, in classifying the size of an animal, we do not 

 go by the height the animal stands, because many animals whose bodies 

 are about the same size differ in height only on account of their legs 

 being longer. In making comparisons, therefore, we compare animals 

 whose bulk is the same, irrespective of the actual height they may 

 stand from the ground. Among the wild animals of a similar size, 

 we also find considerable difference between the comparative size of 

 the brain and that of the body. As an example of this, we may take 

 the case of the lion and tiger. The brain of the lion is much larger 

 than that of the tiger ; however, that might be expected from the lion 

 being a larger animal than the tiger ; but the brain is much larger in 

 proportion than the difference of size of the two animals would account 

 for : therefore the brain of the lion is larger, in proportion to the size 

 of his body, than that of the tiger is in proportion to his body. 



But we must now compare the size of the brains of domestic ani- 

 mals of the same size. Although the horse stands higher than the ox, 

 yet both those animals may be classed together for the comparisons of 

 their brain. We find that the brain of the horse is very much larger 



