MAMMALIA— PHYSIOLOGY 



461 



the ciliary movement is upward towards the throat. Inhalation of 

 chloroform stops ciliary activity, while ether does not (Lucas). 

 Hach found (1925) that morphine slowed the rate of movement 

 of pollen injected into the trachea of dogs, but that caffein increased 

 the speed of its transportation. 



Respiration. — During the first year of life, the average rate of 

 respiration in the human infant is about forty-four per minute. 

 It gradually reduces to a rate of about fourteen or fifteen per minute 

 in the adult. 



Table of Respiration Rates of Various Animals. (Bert ^) 



Hippopotamus i per minute 



Lion 



Horse 



Pig 



Ox 



Dog 



Sheep and goat i 



Cat 24 



Pigeon 30 



Eel 50 



Rabbit 55 



Sparrow 90 



Rat (asleep) 100 



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How Long Can Aquatic Mammals Submerge'^ — It is well known 

 that by practice it is possible for man to remain submerged for over 

 two minutes (see page 157). Parker, in some recent observations, 

 has shown that the Florida manatee can remain submerged sixteen 

 minutes. The whale, reported to submerge for an hour, has been 

 found by Parker to remain twenty minutes under water. 



Voices of Mammals. — In man, the dog, the sheep, and the horse, 

 the voice is produced by expiratory blasts of the lungs producing 

 vibrations of the vocal cords. The pitch of sound and tones depends 

 on the tension of the vocal cords, a low-pitched tone being produced 

 by relaxed cords. In the cat, the pig and cattle, the voice is an 

 inspiratory act. The whale, the dolphin, and the giraffe are mute. 



The Excretory System. — The urinary system of the mammal 

 consists of paired kidneys where solid products of decay that cannot 

 be eliminated by the lungs are excreted in the urine which passes 

 from the kidneys by way of the ureters to the ventrally situated 



^ Dearborn, G. V. N. 1908. Human Physiology. Lea and Febiger, Philadelphia. 



