136 TISSUES IN GENERAL. 



In Lecture I., delivered February 16, 1858, Virchow said: "'If we con- 

 sider the extraordinary influence which Bichat, in his time, exercised upon the 

 state of medical opinion, it is indeed astonishing that such a relatively long 

 period should have elapsed since Schwann made his great discoveries without 

 the real importance of the new facts having been duly appreciated. This has 

 certainly been essentially due to the great incompleteness of our knowledge 

 with regard to the intimate structure of our tissues, which has continued to 

 exist until quite recently, and, as we are sorry to be obliged to confess, still 

 even now prevails with regard to many points of histology, to such a degree 

 that we scarcely know in favor of what view to decide. Especial difficulty 

 has been found in answering the question from what parts of the body 

 action really proceeds, what parts are active, what passive ; and yet it 

 is already quite possible to come to a definite conclusion upon this point, even 

 in the case of parts the structure of which is still disputed. The chief point 

 in this application of histology to pathology is to obtain a recognition of the 

 fact that the cell is really the ultimate morphological element in which there 

 is any manifestation of life, and that we must not transfer the seat of real 

 action to any point beyond the cell." And further on he said: " According 

 to my ideas, this is the only possible starting-point of all biological doctrines. 

 If a definite correspondence in elementary form pervades the whole series of 

 all living things, and if in this series something else which might be placed 

 in the stead of the cell be in vain sought for, then must every more highly 

 developed organism, whether vegetable or animal, necessarily, above all, be 

 regarded as a progressive total, made up of a larger or smaller number 

 of similar and dissimilar cells. Just as a tree constitutes a mass arranged 

 in a definite manner, in which, in every single part, in the leaves as in the 

 root, in the trunk as in the blossom, cells are discovered to be the ultimate 

 elements, so it is also with the forms of animal life. Every animal presents 

 itself as a sum of vital unities, every one of which manifests all the character- 

 istics of life. The characteristics and unity of life cannot be limited to any 

 one particular spot in a highly developed organism (for example, to the brain 

 of man), but are to be found only in the definite, constantly recurring, struct- 

 ure which every individual element displays. Hence it follows that the 

 structural composition of a body of considerable size, a so-called individual, 

 always represents a kind of social arrangement of parts, an arrangement of a 

 social kind, in which a number of individual existences are mutually depend- 

 ent, but in such a way that every element has its own special action, and 

 even though it derive its stimulus to activity from other parts, yet alone 

 effects the actual performance of its duties. I have therefore considered it 

 necessary, and I believe you will derive benefit from the conception, to portion 

 out the body into cell-territories (Zellen-territorien). I say territories, because 

 we find in the organization of animals a peculiarity which in vegetables is 

 scarcely at all to be witnessed, namely, the development of large masses of 

 so-called intercellular substance. Whilst vegetable cells are usually in imme- 

 diate contact with one another by their external secreted layers, although in 

 such a manner that the old boundaries can still always be distinguished, we 

 find in animal tissues that this species of arrangement is the more rare one. 

 In the often very abundant mass of matter which lies between the cells 

 (intermediate, intercellular substance) we are seldom able to perceive at a 

 glance how far a given part of it belongs to one or another cell ; it presents 

 the aspect of a homogeneous intermediate substance. According to Schwann, 



