HIBEENATION, KTO., IN ANIMALS. 63 



respiratory luoveineuts; but iu the woodehuck I uever l'ail lo notice llioiii at ronssiderahli' 

 intervals, say ouce in five to iiiue minutes, even when hibernating most protbuncUy. 

 The respirations were peculiar. Sometimes one deep inspiration preceded by a sudden 

 relaxation of the enlarged chest would be succeeded by a long pause ; again there would 

 be a series of very slight respiratory movements. It was always possible by the respira- 

 tions alone to predict when the animal was approaching the waking state. 



The awakening was uever sudden but gradual, often extending over hours. I have 

 seen something like this though less remarkable in the bat. This is no doubt protective 

 to the vital machinery, for when Hall maintained that bats suddenly awaked from the 

 hibernating condition died speedily, he was iu the main, if not entirely cori'eot. 



A brief consideration of natural daily sleep will throw light on winter sleep, etc. 



Sleep is favoured by moderate exhaustion, a good condition of nutrition and the ab- 

 sence of all sorts of peripheral stimuli 



The case of the youth having but one good eye and one hearing ear who could be 

 put to sleep by closing these up is very instructive. This lad did not however continue 

 to sleep indefinitely, but awoke after a number of hours, showing that though there are 

 certain conditions in the environment that favour sleep, the latter is essentially a condi- 

 tion of the central nervous system and dependent on laws governing the latter. This 

 view makes its clear that sleep is naturally a nocturnal condition for most animals, 

 owing, no doubt, to the evolution of life in relation always to the environment. The 

 fact is we cannot conceive of life except iu and by reason of, in a sense, some environ- 

 ment. The change of the seasons, day and night, and all the periodicities of the inor- 

 ganic world have as a natural consequence stamped themselves on living things, plants 

 as well as animals. Sleep then is essentially a rhythmic diminution of the activities of all 

 the tissues, but especially of that one, which controls all others, the nervous. Rhythm 

 seems to be at the ba.sis of all things organic and inorganic, but has not been enough 

 considered in our explanation of living cells. It was long the custom to explain sleep 

 by auœmia of the brain, whereas the very antT?mia was due to a contraction of the blood 

 vessels of the part accompanied by the diminution of the heart-beat, both of which arc 

 periodical and dependent on the rhythm of the nervous system itself. Of course, tempo- 

 rary anaemia of the brain favours sleep, though it is not the essential cause. As a natural 

 consequence of the decline in the activity of the great controller of the cell activities (me- 

 tabolism) /. e., the nervoirs centres, it is found that all the functions of the body without 

 exception perhaps are diminished during sleep. Marshall Hall and others since his time 

 have shown that the gaseous interchange in a hibernating animal is greatly lessened. 

 This diminished metabolism explains why the animal does not recjuire to eat, or but little. 

 It explains the diminished excretions, etc., etc. 



This being understood it is not surprising that liiberuatiug animals may be kept 

 under water for long periods as is the case with newly-born mammals as kittens and 

 puppies, whose vital machinery as yet works very slowly, which are in fact in a condition 

 but slightly more advanced physiologically than the uterine which is a sort of reptilian 

 pre-natal state — as regards the circulation, respiration, etc. 



As the metabolism of reptiles and amphibians is of a much slower kiud than that of 

 mammals it is not surpri.sing that their winter sleej] is more profound. But it is to be 

 observed that the change from their most active to their most sluggish condition is not 

 probably relatively greater than in the case of mammals. 



