PHYSIOLOGY. 



689 



ing upon itself, is able to augment its own elas- 

 ticity and versatility." We may ask, then, "Is 

 not this one of the means, perhaps the princi- 

 pal one, by which the collectivity of living ex- 

 istence becomes a self-improving machine ? . . . 

 if the living being is improved by exercise, 

 does not this also explain the progress of the 

 aggregate?" To this query are apparently 

 opposed the observed facts that only the most 

 highly organized animals are amenable to ex- 

 ercise, and that even these animals do not of 

 themselves exercise and perfect themselves, but 

 do so only when man takes them to school. 

 To these it is replied that the lower animals 

 and the higher animals in their natural state 

 have already acquired, perhaps by the aid of 

 exercise, in their instincts, all the faculties they 

 require for the maintenance of their species, 

 and there is no room under those conditions 

 for further improvement or for development 

 in new directions. " Susceptibility to exercise 

 first enters into the animal world when the 

 maintenance of the individual and the species 

 has been so assured, through outer and inner 

 circumstances, that the creature does not need 

 a further particular one-sided development." 

 Improvement by natural selection must be con- 

 sidered as a co-factor with improvement by 

 exercise, in explaining the adaptability of or- 

 ganic nature ; and if we do not concede " that 

 the adaptive quality originated otherwise than 

 mechanically, we must conclude that in the 

 struggle for existence those creatures prevailed 

 which, by the exercise of their natural func- 

 tions, casually increased their fitness for those 

 functions, or did this more than others, and 

 that the beings so favored transmitted this 

 their happy gift to their posterity for further 

 increase. Thus originated an animal world sus- 

 ceptible of exercise ; thus was originated nat- 

 ural selection itself, in the exercise of an im- 

 portant aid ; finally, thus became the whole 

 of life, like the individual, a self-improving ma- 

 chine." 



EXERCISE DURING INFANTILE DEVELOPMENT. 

 The practical question whether systematic 

 exercise should be employed for the physical 

 development of infants and young children has 

 been frequently asked, and has received con- 

 siderable attention, with some attempts to de- 

 vise methods for the purpose, but as yet with 

 no very satisfactory results. In considering 

 the form of exercise that might be employed 

 for very young children, it should be remem- 

 bered that at no period in life does the organ- 

 ism exhibit greater developmental activity than 

 during the first years of existence. Hence it 

 is not advisable that fatigue should be allowed 

 to depress the vital powers, and so interfere 

 with the processes of growth and nutrition. 

 At the same time, it must be borne in mind 

 that a desire for exercise seems to be inherent 

 in the infant. This becomes apparent at a 

 glance when a healthy young child is stripped 

 and laid on a bed, leaving the body and limbs 

 unhampered. Its movements are almost cease- 

 VOL. xxii. 44 A 



less ; all parts of the body are brought into 

 play, until it seems as if the child were trying 

 to turn itself inside out ; and, at the same time, 

 the look of satisfaction which overspreads the 

 countenance shows that the operation is thor- 

 oughly enjoyed. This natural exercise should 

 be encouraged, and, instead of being kept, as 

 it too frequently is for the greater part of the 

 day, tightly held in its nurse's arms, or con- 

 fined in its cot, weighed down with heavy 

 bed-clothes, which restrain its slightest move- 

 ment, the child should for some time each day 

 be allowed to roll freely on a mattress, lightly 

 and loosely clad, so that it can indulge freely 

 and unhampered in the natural and instinc- 

 tive exercise of its limbs. As it gets older 

 the desire for exercise seems, if possible, to 

 increase, and it is never tired of creeping 

 about and making premature attempts to walk. 

 While these efforts should be encouraged, they 

 should never be unduly prolonged. As the 

 child grows older, and becomes firmer on its 

 feet, combined movements seem to become 

 its object, and these also may profitably be 

 encouraged. But artificial provisions for ex- 

 ercise are best dispensed with until after the 

 sixth or seventh year. What seems of most 

 importance, and what, unfortunately, is most 

 generally overlooked, is the necessity of secur- 

 ing for the young child complete freedom of 

 all its movements, and thus permitting it to 

 engage in spontaneous exercise without let or 

 hindrance. 



ORIGIN AND DESTINY OF THE FAT-CELLS. 

 Professor Simon F. Gage, of Cornell University, 

 has published an account of some microscopic 

 investigations he has made to ascertain the 

 origin and destiny of the fat-cells. His obser- 

 vations were made upon the Necturus, or Me- 

 nobranchus, a perennibranchiate amphibian 

 of the lakes of Western New York. Micro- 

 scopic investigations have unmistakably shown 

 that the fat of the body does not exist free, 

 but in small, circumscribed masses, composed 

 of protoplasmic cells simply holding fat in 

 readiness for the use of the system. Two 

 theories had prevailed with respect to the ori- 

 gin of these "cells: one, held by Von Wittig, 

 Virchow, and others, that they are fixed or 

 branched connective-tissue corpuscles modified 

 into fat-cells ; the other, supported by Eanvier, 

 Hoggan, and others, that they are developed 

 from special plasma cells, or from the migra- 

 tory corpuscles become quiescent for the time. 

 The result of Professor Gage's investigations 

 appears to establish the fact that branched 

 connective-tissue cells become fat-cells by be- 

 ing partly or wholly gorged with fat ; and also 

 makes it plausible, from the presence of fat in 

 the small unbranched cells, that migratory cor- 

 puscles may become quiescent and assume the 

 duties of fat reservoirs. Thus the two theories 

 are harmonized, and both are shown partly to 

 include the truth. The destiny or purpose 

 of the fat-cell is to be a reservoir, serving 

 to hold a store for the future use of the animal : 



