128 Dynamic Theory. 



The animal functions and activities, including consciousness and all 

 the conscious actions, are supplementary, in the animal economy, to 

 the vegetative functions, and are, consequently, of secondary importance. 



The normal remedy of nature for vital exhaustion is the suspension 

 of these animal functions temporarily. This is done every day in sleep. 

 During sleep the waste of brain, ' nerve and muscle tissue is largely sus- 

 pended, and whatever surplus remains to the vegetative organs after 

 their own nourishment is secured, is transferred to the repairs of the 

 animal organs. But if during sleep there is no surplus of food and 

 energy above what is required for the vegetative parts of the organism, 

 the animal parts may remain unrenewed indefinitely, or until their func- 

 tions are required to assist in securing a new supply of food for the 

 vegetative parts. But as long as the vegetative functions can run with- 

 out the animal functions they will do it, and the sleep will continue. 

 When the organic sj'stem is subjected to a temperature either above or 

 below the normal, more or less exhaustion ensues, and the tendency is 

 to curtail expenses by cutting short the supply to the animal functions. 

 So we find lethargy and sleep induced by both the cold of winter and 

 the heat of summer. Everybody can testify to experimental knowledge 

 of this, although the human race has become largely independent of 

 the weather. Exposure to the cold of a chilly day is succeeded by 

 drowsiness. A slight lowering of the temperature in the tropics makes 

 the natives sleepy. All the warm blooded animals are made sleepy by 

 the cold, and many of them sleep most of the winter in the temperate 

 climates among these are the Bear, and most other Plantigrades, Bat, 

 Hedgehog, Zizil, Marmot, Dormouse, Hamster, Ground-squirrel, &c. 



In some, the temperature is reduced, almost to freezing, as in the 

 Zizil and Marmot, whose temperature goes as low as 43 F. , the waking 

 temperature being 101 to 103 F. 



Nearly all the cold blooded land animals, as Snakes, Toads, Lizzards, 

 &c. , also Turtles, Eels and Insects, are rendered torpid by the cold, 

 their temperature generally keeping near that of the air. Reptiles and 

 Amphibians at best live very low and slow, their respiration and diges- 

 tion being very inactive. In the winter sleep both are reduced to a 

 minimum. 



All of us can likewise testify to the drowsy effect of summer heat. 

 Our fellow creatures are affected in the same way, and man}* of them 

 make a season of it by going into a summer sleep. The Tenrec of Mad- 

 agascar, a relative of the Hedgehog, does this, and so do numerous in- 

 sects, spiders, snails, toads and lizzards, the Crocodile in some coun- 

 tries, and most of the land Mollusks around the Mediterranean Sea. 



Exhaustion of tissue may proceed from two causes: overwork, and 

 under-feeding of the tissue. When the system is contending against 



