Before all things, chemists lack a clear and rational idea of their science, of its relation to the sciences which stand nearest to it and the way in which its problems should be stated. Being intermediate between physics and biology, chemistry has suffered from the vicinity of both. As the more advanced sciences always have a marked tendency to encroach upon those above them, chemistry must in the first place defend itself against the ascendency of physics, as physics itself must fight against that of mathematics. The chemist must undoubtedly have studied physics, in order to make use of the results obtained by this science, and to turn them, if he can, into a method for his own use. The relation of these two sciences is very close, and a knowledge of the laws of calorific and electric phenomena, for instance, is of the highest importance for chemical research. But, for all this, the chemist has his own point of view. He studies, (which the physicist does not do), the laws of the phenomena of composition and decomposition which are the result of the molecular and specific action of diverse natural or artificial substances upon each other. He must therefore make use of physics, but not subordinate himself to it. On the other hand physiological research is not within the province of chemistry. What has been called “biological chemistry” belongs, according to Comte, to biology alone. For the physiologist to have gone through the school of chemistry is natural and even indispensable. But his point of view is quite different from that of the chemist. As a matter of fact, chemists have shown themselves unqualified for physiological studies. None of their numerous attempts have succeeded in establishing a single point of general doctrine, in biology. They merely furnished materials. Moreover these cannot be used just as they are by the physiologist, who is obliged to take up the researches again “under the preponderating influence of biological considerations.” Comte admires the self-confidence of the chemists who approach physiological questions without having measured or even suspected the special difficulties. It is, however, clear that the most carefully made chemical analyses must be fruitless here so long as they are not directed in the first place by a precise physiological notion of the whole of the phenomenon, and then modified by the knowledge of the limits of the normal variations to which the phenomena may be liable. Now, for proceeding in this manner, the physiologists alone are competent.[142]