305 



SCIENTIFIC SIDE-LIGHTS 



Heredity 



cms external agencies or accidents, might be 

 transmitted to their offspring. [See DEVI- 

 ATION'S INHERITABLE.] GILL Address in 

 Memory of Edward Drinker Cope in Pro- 

 ceedings of Amer. Assoc. for Advancement 

 of Science, vol. xlvi, 1897. 



1485. 



Epileptic Guinea- 



pigs. A very curious example of the trans- 

 mission of tendencies to special automatic 

 movements, the secondary acquirement of 

 which tendencies is altogether beyond doubt, 

 is afforded by the following curious fact es- 

 tablished by the researches of M. Brown- 

 Sequard: In the course of his masterly ex- 

 perimental investigations on the functions 

 of the nervous system, he discovered that, 

 after a particular lesion of the spinal cord 

 of guinea-pigs, a slight pinching of the skin 

 of the face would throw the animals into a 

 kind of epileptic convulsion. That this arti- 

 ficial epilepsy should be constantly produ- 

 cible in guinea-pigs, and not in any other 

 animals experimented upon, was in itself 

 sufficiently singular; and it was not less 

 surprising that the tendency to it persisted, 

 after the lesion of the spinal cord seemed to 

 have been entirely recovered from. But it 

 was far more wonderful that when these 

 epileptic guinea-pigs bred together, their 

 offspring showed the same predisposition, 

 without having been themselves subjected 

 to any lesion whatever; whilst no such 

 tendency showed itself in any of the large 

 number of young, which were bred by the 

 same accurate observer from parents that 

 had not thus been operated on. CARPENTER 

 Mental Physiology, ch. 8, p. 371. (A., 

 1900.) 



1486. 



How Limited. 



In [many] exercises of [animal] intelligence 

 we may trace the manifestations of a 

 hereditary transmission of aptitudes for 

 particular kinds of mental action which 

 have been originally acquired by habit. 

 Dogs of other breeds cannot be taught to 

 herd sheep in the manner which " comes 

 naturally" to the young of the shepherd's 

 dog. And it is well known that young 

 pointers and retrievers, when first taken 

 into the field, will often " work " as well as 

 if they had been long trained to the require- 

 ments of the sportsman. The curious fact 

 was observed by Mr. Knight that the young 

 of a breed of springing spaniels which had 

 been trained for several successive genera- 

 tions to find woodcocks, seemed to know as 

 well as the old dogs what degree of frost 

 would drive the birds to seek their food in 

 unfrozen springs and rills. Among the de- 

 scendants of the dogs originally introduced 

 into South America by the Spaniards there 

 are breeds which have learned by their own 

 experience, without any human training, the 

 best modes of attacking the wild animals 

 they pursue; and since young dogs have 

 been observed to practise these methods the 

 very first time they engage in the chase, 

 with as much address as old dogs, it can 



scarcely be questioned that the tendency to 

 the performance of them has been embodied 

 in the organization of the race, and is thus, 

 transmitted hereditarily. There seems rea- 

 son to believe that such hereditary trans- 

 mission is limited to acquired peculiarities 

 which are simply modifications of the nat- 

 ural constitution of the race, and would not 

 extend to such as may be altogether foreign, 

 to it. But the foregoing facts would seem 

 to justify the belief that the like hereditary 

 transmission of acquired aptitudes may take 

 place in man; and that, in accordance with 

 the far wider range of his faculties, it may 

 become the means of a far higher exaltation 

 of them. CARPENTER Mental Physiology, 

 ch. 2, p. 102. (A., 1900.) 



1487. 



Inherited Effect of 



Changed Habits. Changed habits produce 

 an inherited effect, as in the period of the 

 flowering of plants when transported from 

 one climate to another. With animals the 

 increased use or disuse of parts has had a 

 more marked influence; thus*"! find in the 

 domestic duck that the bones of the wing 

 weigh less and the bones of the leg more, in 

 proportion to the whole skeleton, than do- 

 the same bones in the wild duck; and this, 

 change may be safely attributed to the do- 

 mestic duck flying much less, and walking 

 more, than its wild parents. [See INHERIT- 

 ANCE.] DARWIN Origin of Species, ch. 1, p. 

 10. (Burt.) 



1488. Mental Habitudes 



Transmitted as Tendencies. Now, as there 

 can be no doubt of the hereditary trans- 

 mission in man of acquired constitutional 

 peculiarities, which manifest themselves 

 alike in tendencies to bodily and to mental 

 disease, so it seems equally certain that 

 acquired mental habitudes often impress 

 themselves on his organization with suffi- 

 cient force and permanence to occasion their 

 transmission to the offspring as tendencies 

 to similar modes of thought. And thus, 

 while all admit that knowledge cannot thus 

 descend from one generation to another, an 

 increased aptitude for the acquirement, 

 either of knowledge generally, or of some 

 particular kind of it, may be thus inherited. 

 These tendencies and aptitudes will acquire 

 additional strength, expansion, and perma- 

 nence in each new generation, from their 

 habitual exercise upon the materials sup- 

 plied by a continually enlarged experience; 

 and thus the acquired habitudes, produced 

 by the intellectual culture of ages will be- 

 come a " second nature " to every one who 

 inherits them. CARPENTER Nature and Man, 

 lect. 6, p. 197. (A., 1889.) 



1489. 



New Instincts the 



Result of Changed Circumstances. This ex- 

 planation of the origin of the migratory 

 instinct, and the reason why birds take 

 certain determinate routes over the sea, is 

 in perfect agreement with the conclusion 

 at which Mr. Darwin arrived at an even 

 earlier date, tho the facts were not pub- 



