348 THE HISTORY OF BIOLOGY 



His classification of tissues 

 According to Bichat's classification, the body is built up of tissues, which 

 may be grouped in systems — for example, the bone system, the cartilage 

 system, the muscle system. An organ is composed of several systems (e.g., the 

 stomach, the lungs, the brain); several organs form an apparatus (e.g., the 

 respiratory apparatus, the digestive apparatus). The knowledge of the tissue 

 systems forms what Bichat calls "general anatomy," which he discusses in 

 an important work;- upon this knowledge should be based the theory of 

 organs or, as he calls it, descriptive anatomy. Bichat claims that this method 

 of research and investigation is new, for, as he adds with justifiable self- 

 appreciation, general anatomy hardly existed before he produced his works 

 on the subject. 



The tissues, Bichat declares, are the true conservators of the life of the 

 body. He distinguishes between twenty-one diff^erent kinds of tissues — ■ 

 namely, (i) cellular (closely corresponding to what is now called retiform 

 connective tissue); (z) the nervous tissue of animal life; (3) the nervous 

 tissue of organic life; (4) arterial; (5) venous; (6) the tissue of exhalation; 

 (7) absorbent; (8) bone-tissue; (9) medullary tissue (in the bones); (10) 

 cartilaginous; (11) fibrous; (li) fibrocartilaginous; (13) animal musculature; 

 (14) organic musculature; (15) mucous tissue; (16) serous; (17) synovial; 

 (18) glandular; (19) dermoid; (xo) epidermoid (dermis and epidermis); 

 (21) capillary tissue. These tissues, however, are by no means alike every- 

 where; rather, they invariably possess the power to adapt themselves to the 

 organs in which they are incorporated. The tissues are the true conservators 

 of life; not each individual organ, as Bordeu asserted, but each individual tis- 

 sue has individual life. Therefore diseases, in so far as they attack individual 

 organs, are localized in their tissues; in abdominal catarrh it is the mucous 

 membrane that is affected and not the m.uscles in the abdominal wall; in 

 inflammation in the brain it is in most cases the cerebral membrane that is 

 the seat of the disease. "If we would study a bodily function, we must con- 

 sider the organ which performs that function from a general point of view, 

 but if we would become acquainted with the vital qualities of the organ, we 

 must disintegrate it" — that is, into the tissues of which it is formed. The 

 tissues are thus the vehicles of life; in maintaining this view Bichat definitely 

 dissociates himself from a number of earlier and contemporary scientists, 

 who considered the fluids to be the true vital elements of the body.^ But the 

 vital qualities are not identical with the actual structure, for this still 

 remains after life has departed; not even the fluids of the body are the same 

 after death, and if we analyse them chemically we find only an equivalent 



^ The Traiti des membranes, cited in the bibliography, may be regarded as a preliminary 

 study to this work. 



' See, for instance, Sommerring's above-mentioned theory on the cerebral fluids. 



