yune I, 1876] 



NATURE 



117 



forms of crystals, and ihe method of notation best adapted 

 for international use, will probably be discussed in the 

 Conterence. 



I have thus briefly touched upon some of the salient 

 points which occur to the mind when taking a cursory view 

 of an Exhibition such as the present. In doing so I have 

 no doubt passed over many instruments and appliances 

 of even greater importance than those which I have thus 

 succinctly mentioned, and have probably left untouched 

 many topics of the highest interest. Among the subjects, 

 however, which will be discussed on each day of our Con- 

 ferences there will, I hope, be a sufficient variety to give 

 occasion for. any one to call attention to any special 

 features of novelty in the collection. What I have ven- 

 tured to say must be regarded as merely a short intro- 

 duction to communications of far greater value, from 

 which I will no longer detain you. 



SECTION— BIOLOGY 



Opening Address by the President, Prof. J. Burdon 

 Sanderson, M.D., LL.D., F.R.S. 



It having been made a part of the duty of the chairman 

 of each of the sections into which this Exhibition is divided 

 to deliver an opening address, I had no difficulty in select- 

 ing a subject. I propose to place before you a short and 

 very elementary account, addressed rather to those who 

 are not specially acquainted with biology than to those 

 who are devoted to the science, in which I shall give you 

 a description of a few of the methods which are used in 

 biological investigation, particularly with reference to the 

 measurement and illustration of vital phenomena. You 

 are aware that the Committee, in order to render these 

 conferences as useful as possible, have thought it desirable 

 that we should devote our attention chiefly to those subjects 

 of which the instruments in the collection contribute the 

 best examples. 



Now these subjects are, first, the methods of registering 

 and measuring the movements of plants and animals ; 

 secondly, the methods of investigating the eye as a phy- 

 sical instrument ; and thirdly, the methods of preparing 

 the tissues of plants and animals for microscopical exami- 

 nation. Of these several subjects it is proposed we should 

 to-day concern ourselves chiefly with the first. I will 

 therefore begin by endeavouring to illustrate to you some 

 of the simplest methods of physiological measurement, 

 particularly with reference to the time occupied in the 

 phenomena of I'fe, leaving the description of more com- 

 plicated apparatus to Prof. Bonders, who will address you 

 on Monday, and to my friend. Prof. Marey, who is with 

 you now, and who will give you an account of some of the 

 beautiful instruments which he has contrived for this 

 purpose. 



The study of the life of plants and animals is in a very 

 large measure an affair of measurement. To begin, let me 

 observe that the scientijic study of nature, as contrasted 

 with that contemplation of natural objects which many 

 people associate with the meaning of the word " natu- 

 ralist," consists in comparing what is unknown with what 

 is known. Whatever may be the object of our study — 

 whether it be a country, a race, a plant, or an animal, it 

 makes no difference in this respect, that the process in 

 each of these cases is a process of comparison, a process 

 in which we compare the object studied in respect of 

 such of its features as interest us, with some known 

 standard, and the completeness of our knowledge is to be 

 judged of in the first place by the certainty of the standard 

 which we use ; and secondly, the accuracy of the modes 

 of comparison which we employ. Now, when you think 

 of it, comparison with a standard is simply another ex- 

 pression for measurement ; and what I wish to impress 

 is, that in biology, comparison with standards is quite as 

 essential as it is in physics and in chemistry. Those of 



you who have attended the conferences on those subjects 

 will have seen that a very large proportion of the work of 

 the physical investigator consists in comparison with 

 standards. From his work, our work, however, differs in 

 this respect, that whereas he is very much engaged in 

 establishing his own standards and in establishing the 

 relations between one standard and another, we accept 

 his standards as already established, and are content to 

 use them as our starting-point in the investigation of the 

 phenomena which concern us. 



Now I wish to illustrate this by examples. The first 

 objects which strike the eye on entering this collection— 

 the collection in the next room — are certainly the micro- 

 scopes. But you will say, surely the microscope cannot 

 be regarded as an instrument of measurement. In so far 

 as it is an instrument of research and not merely a pas- 

 time, it is emphatically an instrument of measurement, 

 and I will endeavour to illustrate this by referring to one 

 of the commonest objects of microscopic study, namely, 

 the blood of a mammalian animal. Now as regards the 

 blood I will assume that everybody knows that the 

 blood is a fluid mass, in which solid particles float. 

 With reference to the form of those particles, all that 

 we see under the microscope is merely a circular outline. 

 If we wish to find out what form that represents we 

 must use methods which are really methods of measure- 

 ment. By the successive application of such methods 

 we learn that this appaiently circular form really cor- 

 responds to a- disc of peculiar biconcave shape. But 

 I will not dwell more upon the application of mea- 

 surement to the form of the corpuscles, but proceed at 

 once to a subject that can be illustrated by an instrument 

 before you for ascertaining the number of the corpuscles. 

 It will be obvious to you — even to those who are not 

 acquainted with physiology and pathology— that the 

 question of the proportion of corpuscles which are 

 contained in the blood must be a matter of very 

 great importance to determine. It has been long 

 known that the colouring matter which is contained 

 in the corpuscles is the most important agent in the 

 most important vital processes of the body, because it is 

 by means of it that oxygen, which is necessary to the life 

 of every tissue is conveyed from the respiratory organs to 

 the tissues. This being the case, it is evidently of very 

 great importance both to the pathologist and to the man 

 who interests himself in investigating the processes of 

 nature, to be able to determine accurately vrhat proportion 

 of corpuscles the blood contains. Well, there are chemi- 

 cal methods of doing this. We can do it by determining 

 how much iron the blood contains, because we know that 

 the proportion of iron in the corpuscles is always nearly the 

 same, and by determining the quantity of iron chemically, 

 we can find out how many corpuscles there are in a cer- 

 tain amount of blood. But this is a long process, 

 requiring first the employment of a considtrable quan- 

 tity of blood, and secondly, difficult chemical mani- 

 pulations and a long time. Now by a method which 

 has been very recently introduced, we have the means of 

 applying the microscope even to a single drop of blood, 

 to a drop such as one could obtain by pricking one's finger 

 at any moment, or could take, in this way, from any patient 

 in whom it might be desirable to ascertain the condition 

 of the blood as regards the number of its solid particles. 



The method consists in this. In order that you may 

 understand it I will ask you to fix your attention upon 

 this cube which I draw on the board. Suppose this cube 

 is not of the size actually represented, but that it is a cube 

 of one millimetre, i.e., the ^ part of an inch. How many 

 blood corpuscles do you suppose are contained in a cube 

 of that size .'' Such a cube we know to contain in normal 

 blood about 5,000,000 corpuscles. Supposing we had a 

 method by which we could count those 5,000,000 particles 

 it is obvious that the task would be endless, and even if 

 we were to take a cube x\t P^rt of that size, namely, a 



