WHALES AND PORPOISES 23 



They depend upon the air for breathing, like any other animal, and would 

 drown if kept below water too long. Some can only stay an hour, others as 

 long as twelve hours, beneath the sea. Once, in the ages long past, they had 

 legs ; but of these no vestige remains to-day except some very small frag- 

 ments of bones to be found in the lower muscles. These are said to be the 

 remains of the thigh and one of the leg bones. Their fore-limbs, or flippers, 

 are really hands in those species that possess teeth, being five-fingered, 

 whilst in those that have plates of baleen, or whalebone, in place of teeth, 

 they are four-fingered. 



Whales are encased in a thick padding of blubber, which serves to keep them 

 warm in Arctic seas, and also acts as a cushion, protecting the body from the 

 pressure of the water when they dive deep. They have no ears, but small 

 holes in the head which answer the same purpose. Some species have one 

 nostril, and others two, through which they breathe. When they exhale the 

 vast bulk of air from their lungs after having been submerged, the moisture 

 from the lungs condenses into vapour, and produces an appearance called 

 " spouting." A whale does not throw up water in a regular fountain, as so 

 many old pictures represent ; but just as human breath becomes visible on 

 a frosty morning, their exhalation looks almost like a fountain of spray. 



Their food consists of many of the crustaceans the young of crabs, shrimps, 



those in front, called incisors, which have a sharp edge ; those at the back, which are molars or 

 grinders, because with them we masticate our food ; and between them come the sharp-pointed 

 " dog " teeth, or canines. These three kinds are represented in much-modified forms in the other 

 mammals. In the Carnivores such as the Cat, for instance the incisors are small, but the canines 

 are very long and pointed, since with these the animal seizes its food. The molars are ill-adapted 

 for grinding, being sharp and pointed. Such mammals cannot "chew" their food, but bolt it 

 in pieces, to be digested after swallowing. 



A Ruminant, such as a Cow or Sheep, has good incisors, but only in the lower jaw ; they 

 meet upon a pad of gristle in the upper jaw, by means of which the vegetable food is torn ; the 

 other teeth are specially formed, as we should expect, for grinding. 



Another noticeable difference between Carnivores and Herbivores will be found in the fact 

 that the former can only move their jaw up and down ; the latter can move it sideways : the 

 reason is obvious. 



The Rodents have an entirely different arrangement of teeth. The incisors are very long 

 and sharp ; there are no canines, and but a few smallish molars. The front teeth are specially 

 formed for their work of gnawing, and are kept sharp by actual exercise. If anything happens so 

 that a Rat or Rabbit loses one of its incisors, the consequences are very serious, as the opposite 

 tooth grows, unchecked, and may at last become so big as to prevent the animal from eating at all ! 



This very general description will serve to suggest to young students the lines upon which 

 they may study the mammals. But in addition, of course, attention must be paid to the forma- 

 tion of the limbs, hoofs, claws, fingers, toes, and so forth. Interesting questions will at once arise, 

 which a little thought will answer, as, for instance : Why does a cat turn its head on one side when 

 eating ? Why are a dog's claws blunt, and a cat's not ? Why are a rabbit's eyes at the side of 

 its head, and so large and staring ? 



A collection of the skulls of the smaller mammals and birds is of no small value for purposes 

 of comparison. To prepare a skull or, for that matter, a skeleton the specimen should be first 

 skinned. Make an incision from the vent upwards, and press the skin back, so that, if properly 

 done, it comes off like a glove. Open the abdomen and take away as much flesh as possible ; and 

 place the body that is left in a vessel of water in the open air. Here it must remain until the rest 

 of the flesh has decomposed and loosened. Examine it from time to time, and when possible take 

 away, with a small brush, what softer portions you can. 



