Indirect Evidence.

From these limited but cogent pieces of evidence I turn to the larger but confirmatory lines of indirect evidence and inference, of which such works as those of Professors Sherrington, Bayliss, and Starling, the notable address of Professor Macdonald at Portsmouth in 1911, as well as the recent work of Professor Woods Jones on Arboreal Man, are full. Indeed if the construc­tion of new reflexes and reflex-arcs in organic evolution “forged by an incident of use” as Professor Macdonald puts it, were expunged from these works, their treatment of the physiology of the central nervous system of higher animals would be emasculated, to say the least of it. And yet not one of these eminent men is writing ad hoc, or for the confusion of Weismann and his followers. At this point it may perhaps gain for the remaining pages a little more considera­tion from opponents if I give a few quotations from these writers in support of the foregoing statement—perhaps the breeze of authority may then carry my little bark a little further on its perilous voyage. Professor Sherrington remarks on the first page of his well known work, in reference to the cell-theory, “with the progress of natural knowledge, biology has passed beyond the confines of the study of merely visible form, and is turning more and more to the subtle and deeper sciences that are branches of energetics. The cell-theory and the doctrine of evolution find their scope more and more, therefore, in the problems of function, and have become more and more identified with the aim and incorporated among the methods of physiology.” Again, “Mere experience can apart from reason mould nervous reactions in so far as they are plastic. The ‘bahnung’ (or facilita­tion) of a reflex exhibits this in germ.” He uses more than once the pregnant phrase, “The canalizing force of habit”; again, “Progress of knowledge in regard to the nervous system has been indissolubly linked with the determina­tion of function in it.” Speaking of the receptive-field he says of the central nervous system, “To analyse its action we turn to the receptor organs, for to them is traceable the initia­tion of the reactions of the centres”; of the extero-ceptive field he says, “facing outwards on the general environment it feels and has felt for countless ages the full stream of the varied agencies for ever pouring upon it from the external world,” page 20, and “each animal has experience only of those qualities of the environment which as stimuli excite its receptors, it analyses its environment in terms of them exclusively. The integra­tion of the animal associated with these leading segments can be briefly with partial justice expressed by saying that the rest of the animal, so far as its motor machinery goes, is but the servant, of them. Volitional movements can certainly become involuntary, and conversely, involuntary movements can sometimes be brought under the subjec­tion of the will. From this subjec­tion it is but a short step to the acquisi­tion of co-ordinations which express themselves as movements newly acquired by the individual,” and, “The integrating power of the nervous system has, in fact, in the higher animal more than in the lower, constructed from a mere collec­tion of organs and segments a functional unity, an individual of more perfected solidarity,” also “a single momentary shock produces in the nervous arc a facilitating influence on a subsequent stimulus applied even 1400σ later.” I will give but one more statement from this work which seems to tell against my humble position of initiative in evolution. Professor Sherrington says at the end of his book, speaking of the adjustments of nervous reactions in the lifetime of the individual: “These adjustments though not transmitted to the offspring yet in higher animals form the most potent internal condition for enabling the species to maintain and increase in sum its dominance over the environment in which it is immersed.” A little care in reading the foregoing chapters will show that this in no way contradicts the views expressed.