Sept. 26, 1889] 



NATURE 



521 



days before and after the eclipse and several hours before 

 sunrise and after sunset. If observations show that the 

 brightness of the zodiacal light is materially diminished 

 during totality, in any part of the region where the moon's 

 shadow darkens the atmosphere, this will go far to show 

 that the zodiacal light originates in the earth's atmo- 

 sphere ; but if, as seen through the shaded air, the zodi- 

 acal light appears brighter than ever, it vvould follow that 

 its location is far from us, and that it is an appendage of 

 the sun. 



(4) The observers of the zodiacal light should not fail 

 to record the phenomena sometimes seen on the opposite 

 side of the horizon, and called Gei^eiischein, or the anti- 

 zodiacal light. Similarly, observers of the twilight phe- 

 nomena should record the appearances in the horizon at 

 the opposite side of the sun, or the so called anti-twilight 

 arc, or band. 



(5) Observers to whom the sun is beyond the horizon, 

 and for whom the atmosphere between them and the sun 

 is not illumined owing to the presence of the moon's 

 shadow, will have a good opportunity, for a few minutes, 

 to see any faint comet that may have been hidden to 

 astronomers by the glare of the sunlight, and, if such 

 should be seen, they should record the apparent altitude 

 and azimuth of the nucleus. 



The diagrams I. and III. trace the 'shadow-cone west- 

 ward to South California and eastward to India, but this 

 should not prevent observers still further west on the 

 Pacific, or east over India and Japan, from recording and 

 reporting such phenomena as they may observe. 



Washington, August. Cleveland Abbe. 



THE BRITISH ASSOCIATION. 

 SECTION D. 



BIOLOGY, 



Opening Address by Prof. J. S. Burdon Sanderson, 

 M.A., M.D., LL.D., F.R.SS. L. & E., President of 

 THE Section. 



It has long ceased to be possible in the course of an annual 

 address in Section D to give an account even of the most im- 

 portant advances which have been made during the preceding 

 twelve months in the various branches of knowledge which are 

 now included under the term Biology. One reason is that each 

 of the biological subjects has acquired such vast dimensions ; 

 the other, that the two main branches — Morphology, which 

 strives to explain why plants and animals have assumed the forms 

 and structure which they possess, and Physiology, which seeks to 

 vmderstand how the living organism works — have now diverged 

 from each other so widely as regards subject and method, that 

 there seems to be danger of complete separation of the one from 

 the other. 



From this sundering of sciences which a generation ago were 

 intimately united, however inevitable it may be. Physiology 

 chiefly suffers, as being even to the naturalist less attractive and 

 interesting. The study of form and structure has the great 

 advantage that it brings the observer into direct relation with 

 objects which excite his curiosity without requiring too great 

 an effort to understand them. This was the case even when 

 Anatomy was mainly descriptive, and Zoology and Botany 

 occupied themselves chiefly with classification and with definition 

 of species. How much more is it the case now that Anatomy, 

 Zoology, and Botany have become built into one system, of 

 which the Doctrine of Evolution is the corner stone ! Morpho- 

 logy, the name now given to this system, has, if I am not 

 mistaken, this advantage over all other subjects of scientific study 

 — that while attractive to the beginner, it is perfectly satisfactory 

 to the mature student. It derives its perfectness from its subject 

 —the order of the plant and animal world. For inasmuch as 

 Its fundamental conception is the development of all organisms, 

 however complicated, from elementary forms, and as the theo- 

 retical development of the plant and animal world (in other words 

 the science of morphology), claims to be nothing more than a 

 synthesis of the observed facts of its actual development, the 



science is co-ordinate and onterminous with living nature, and 

 strives after a perfection which is that of nature itself. 



Physiology is without this source of attractiveness. Its first 

 lessons present difficulties to the beginner which, unless he is 

 contented (as, indeed, ordinary students are) to accept as true 

 what he does not understand, are, to say the least, discouraging ; 

 while to the more mature student, who has mastered more or less 

 some part of the subject, it fails to present a system of know- 

 ledge of which all the parts are interdependent and can be 

 referred to one fundamental principle, comparable to that of 

 development or evolution. 



It is easy to understand that this must be so if we consider the 

 present position of the subject, and the nature of the work which 

 the physiologist has to do. That work is of two kinds. He has 

 first to determine what are the chemical and physical endow- 

 ments of living matter in general, and of each of the varieties of 

 living matter which constitute the animal and plant organism in 

 particular. Then, these having been investigated, he has to 

 determine how these processes are localized so as to constitute 

 the special function of each structure, and the relation between 

 structure and process in each case. The order I have indicated 

 is the logical order, bat in the actual progress of physiology 

 this order has not been followed, i.e. there has not been a cor- 

 relation of structure with previously investigated process, for in 

 former days physiologists spoke of assimilation, secretion, con- 

 traction, and the like, as functions of muscles, glands, or other 

 parts, without recognizing their ignorance of their real nature. But 

 now, no one who is awake to the tendencies of thought and 

 work in physiology, can fail to have observed that the best 

 minds are directed with more concentration than ever before to 

 those questions which relate to the elementary endowments of 

 living matter, and that if they are still held in the background it 

 is rather because of the extreme difficulty of approaching them 

 than from any want of appreciation of their importance. 



It is to some of these questions that I am anxious to draw the 

 attention of the Section to-day. I feel that I have set myself a 

 difficult task, but think that, even should I succeed very partially, 

 the attempt may be a useful one. And I am encouraged by the 

 consideration that the interest they possess is one which is 

 common to plant and animal physiology, and that if we really 

 understood them, they would furnish a key, not only to the 

 phenomena of nutrition and growth, but even to those of repro- 

 duction and development, and by the belief that it is in the 

 direction of elementary physiology, which means nothing more 

 than the study of the endowments of living material, that the 

 advance of the next twenty years will be made. 



Nearly fifty years ago, J. R. Mayer's ^ treatise on the relation 

 between organic motion and the exchange of material in living 

 organisms was published in Germany. Although its value was 

 more appreciated by physicists than by biologists, it was in its 

 purpose, as well as in its subject-matter, physiological. In it 

 Mayer showed for the first time that certain functions of the 

 animal body, which up to that time had been considered most 

 vital, are strictly within reach of measurement, i.e. referable to 

 physical standards of quantity. He was even able to demon- 

 strate that those quantitative relations between different kinds 

 of energy which physicists were then only beginning to recog- 

 nize, held good as regards the processes peculiar to the living 

 organism. 



Almost immediately after the appearance of this now cele- 

 brated work, a series of discoveries were made in physiology, 

 which constituted the period we are now considering an epoch. 

 Mayer himself had proved that muscles in doing work and 

 producing heat do not do so at the expense of their own sub- 

 stance. But this fact could not be understood until Bernard 

 showed that sugar is one of the most important constitiients 

 of the blood, and its storage and production a chief function 

 of the liver. Helmholtz next succeeded in proving what Johannes 

 Miiller- had declared to be nearly impossible — namely, that the 

 time occupied by the propagation of a motor impulse from the 

 brain to a muscle could be measured, and showed it to be 

 proportional to the distance traversed. Next, du Bois-Keymond 

 investigated the electrical phenomena of living beings, and mar- 

 shalled them under a physical theory which stood its ground 

 against the severest criticism for more than a generation. And 

 finally, the hydrodynamic principles relating to the circulation, 

 set forth by Dr. Thomas Young in his Croonian Lecture forty 



' J. R. Mayer, " D!e organische Bewegung in ihrem Zusammenhange mit 

 dem Stoffwechsel" (Heilbrcnn, 1845). 

 ^ MiJller's " Physiology," translation of second edition, p. 2i. 



