June 7, 1907] 



SCIENCE 



any given epidemic there are always cer- 

 tain individuals who never contract the 

 disease. They have a certain natural im- 

 munity to that particular disease, and this 

 immunity is due to some physiological 

 peculiarity. So in a field of rusted or 

 mildewed wheat some individual plants 

 show themselves more resistant than their 

 fellows to the species of rust fungus found 

 upon that species of host. By selecting 

 and propagating these immune individuals 

 we may develop an immune race or strain. 

 The problem is not always so simple as here 

 stated. It may happen that a race im- 

 mune to one disease may be very suscep- 

 tible to another, or immunity may be ac- 

 companied by other qualities altogether un- 

 desirable. One might be led to suppose, 

 on reading certain popular articles in- 

 tended to show how new forms of plants 

 are produced, that it is only necessary to 

 imagine an ideal plant and then set to 

 work to create it. Nothing is farther from 

 the truth than this. Nature does some- 

 times produce something new, as a stone- 

 less plum, or a nectarine on a peach tree. 

 But man must take the materials furnished 

 by nature, combine them in new ways, or 

 modify them within limits which are 

 usually soon reached. He can not create 

 a wheat plant immune to rust, nor a water- 

 melon resistant to the wilt fungus. But 

 if nature furnishes a few individuals with 

 the desired qualities, man can propagate 

 the individuals possessing those qualities, 

 and by rigid selection maintain the quali- 

 ties to a high degree. If it is possible to 

 cross the plants with other species or with 

 varieties of the same species, he may be 

 able to combine in the same individual a 

 number of desirable qualities. Having ob- 

 tained these qualities in one individual, he 

 can best conserve them by vegetative prop- 

 agation, such as by grafts, cuttings, bulbs 

 or tubers, according to the habit of the 

 plant propagated. He may care nothing 



whatever about the limits of species or 

 varieties except in so far as their physio- 

 logical relations help or hinder his com- 

 binations. Following MacDougal 's method, 

 it may be possible to produce in plants 

 some new characters. But even if it werq 

 possible to produce in this way really new 

 species, it is hardly within the range of 

 possibility that we could choose before- 

 hand the kind of a species we would pro- 

 duce. It would be a case of 'cut and try.' 

 If the result be a form with desirable 

 qualities, let it be preserved, but if it be 

 worthless, let it die. Nature has repeated 

 this experiment ten thousand times. If we 

 would imitate her we must search out her 

 secrets in the physiological realm. She 

 conceals them well, but is not unwilling to 

 reveal them to him who questions her with 

 a hearing ear, a seeing eye, and a thinking 

 brain, tools which she herself has given 

 him. 



James B. Pollock 

 Univebsitt of Michigan 



A PLEA FOR THE STUDY OF THE HISTORY 

 OF MEDICINE AND NATURAL SCIENCES' 



For a number of years a new current of 

 thought has been gradually coming to the 

 front in the minds of scientific thinkers of 

 the times. The nineteenth century, the 

 mental development of which is now as- 

 sured, has of late been severely criticized 

 for its unhistorical character, and perhaps 

 not without reason. Over this inheritance 

 from the preceding generation a certain 

 dissatisfaction is being more and more 

 keenly felt in the most diverse branches of 

 science. The main trend of the last cen- 

 tury was naturalistic and economic to a 

 marked degree; so much so, that the new 

 methods discovered in natural science, and 



' Read before the American Anthropological As- 

 sociation, at the meeting of the American Asso- 

 ciation for the Advancement of Science, December 

 31, 1906. 



