Comte’s anatomical and physiological philosophy is naturally allied to the science of his time. It is especially connected with the labours of Bichat and of de Blainville. Here again he endeavours to state the problems in the most general form possible. Anatomy should begin by the study of the tissues, to ascend afterwards to the association of several tissues, that is to say, to the organs, and to the associations of several organs, that is to say, to systems. But analysis must not be concerned with the tissue itself. To attempt the passage from this notion to that of the molecule, is to allow the organic to enter into the inorganic philosophy. In biology, the tissue corresponds to what the molecule is in physics. Such, at least, is the doctrine of the _Cours de philosophie positive_. Later on, instructed by Schwann’s works, Comte admits in the _Politique positive_ that the anatomical element is the cell. Be it tissue or cell, there must be a fundamental anatomical element. The simultaneous existence of several elements independent of one another would greatly mar “the admirable unity of the organic world,” and consequently the perfection of biological science. Life is always essentially the same. To this dynamic consideration, there must correspond, in the static order, that of a common basis invariable in its primordial organisation, successively producing, by deeper and deeper modifications, the various special anatomical elements. Similarly, physiology will not be entirely organised until it studies functions (at least the organic functions), throughout the whole chain of living beings, from the vegetable kingdom up to man. This conception of a general physiology leads Comte to dwell, as Claude Bernard will later on, upon the phenomena of life which are common to plants and to animals. Some are better studied in plants and others in animals. But, whether it be animal or vegetable every organism always presents two fundamental functions: 1. the absorption of nutritious materials borrowed from the _milieu_ (the assimilation of these materials and finally nutrition); 2. the rejection of unassimilated materials. However, plants are the only organised beings which live directly upon the inorganic _milieu_.[171] Comte was ignorant of the physiology of fungi.