[7] _Rudolph Virchow_: Die Zellularpathologie in ihrer Begründung auf physiologische und pathologische Gewebelehre. 1 Aufl. Berlin 1858–4 Aufl. 1871. By means of cell pathology _Virchow_ has laid the foundations upon which our modern medical attitude is built and which must remain essentially forever the basis of all future medical thought. Certain critics, lacking in appreciation of the interrelations between things and ignoring the safer and established knowledge, have considered, in view of the unfoldings of the researches on immunity and of serum therapy, that the time of cell-pathology was _passed_ and must be replaced by the humoral-pathological teaching. These ultramodern critics, however, have here completely ignored the fact that, on the one hand, the life of our body is built up from the life of all of the contained cells, for life in our body exists only in the cells; and on the other, a fact not considered by them is that the components of the body fluids originate from vital activity of the cells either directly or indirectly. No result, indeed, of present serology can alter in the least degree the fact that every disease represents only a disturbance of the physiological processes of cell life of the organism and the harmony in their combined workings. Indeed the more recent observations of serology and chemotherapy are so little opposed to cell-pathology that they are in fact only possible when based on the latter. They are only comprehensible then from the unfoldings of cellular pathology. Until quite recently all those effects of external factors on the living substance which consist in excitation, that is, in an increase of their specific vital processes, have always stood in the foreground of all researches and observations on irritability. It was gradually, however, more and more recognized that the depressing influence of stimuli played a great rôle in the vital process of the organism. _Brown_ was acquainted with exhaustion produced by stimuli, and the discussion of “asthenic” diseases, in which the irritability was reduced, occupied an important place in his pathology. That, however, in the normal activities of the organism such depression or lessening of vital manifestation could result from the influence of stimulation, first became clear after the brothers _Weber_[8] in 1846 discovered the inhibitory effects of the galvanic stimulation of the vagus upon the heart. [8] _Eduard Weber_: “Muskelbewegung.” Article in Wagner’s Handwörterbuch der Physiologie, Bd. 3. Braunschweig 1846.