CHEMICAL CEPTORS 115 



are often attended by persistent bleeding, while an 

 equally extensive incision and laceration of the tissues of 

 the mouth results in little inconvenience from bleeding. 

 The persistent bleeding of the lungs in pulmonary 

 tuberculosis is well known and is in accord with the mea- 

 ger phylogenetic experience of this area with trauma. 

 Interesting and relevant is the discovery of Sir Victor 

 Horsley that a bit of raw muscle taken from an ex- 

 ternal part and applied to a bleeding point will quickly 

 arrest hemorrhage. Of interest also is Cannon's dis- 

 covery that the blood of animals in rage shows a higher 

 tendency to coagulate. Rage is the natural accom- 

 paniment of combat, which in turn is the biologic set- 

 ting for laceration and bleeding. Animals in rage show 

 an increased secretion of adrenin ; and adrenin, accord- 

 ing to Cannon, increases the tendency of the blood to 

 coagulate. 



A further adaptation favorable to blood clotting in 

 a lacerated blood vessel is to be seen in the disposition 

 of the slender strands of connective tissue fibers which 

 form the outer layer of the blood-vessel wall. In jury- 

 to the vessel causes these tiny fibers to be thrown 

 athwart the rent in a tangled meshwork, interfering 

 with the flow of the blood and constituting the foreign 

 substance which always facilitates the chemical act 

 of coagulation. 



If coagulation be precipitated by thromboplastin 

 (Howell), then one ought to find an uneven distribu- 

 tion of thromboplastin in the various tissues of the 

 body corresponding to the variations in the coagulation 

 times in those parts. This point was partially tested 

 in a research in my laboratory by means of Ho well's 



