6 



Scientific Proceedings (77). 



later, the fibrin becomes transformed into permanent collagen 

 fibrils such as are found in the healed scar. This view is so at 

 variance with that generally held that a careful review of the 

 work seems desirable. 



The changes in the fibrin referred to may be briefly described. 

 When the tissue culture is first prepared the fibrin meshwork of 

 the clot is so delicate that the coagulum appears as a homogeneous 

 almost translucent mass. Within two to five days as the clot 

 contracts there appear in a certain number of the preparations, 

 coarse fibrils sometimes wavy in character which radiate generally 

 from the central fragment of tissue. We have observed this 

 change in clotted fowl, human and rabbit plasma, as well as in 

 frog plasma studied by Baitsell. The formation of these coarse 

 fibrils is evidently the result of the contraction of the clot with 

 fusion of many of the delicate fibrin threads. The change may 

 be facilitated, as Baitsell has pointed out, by mechanical disturb- 

 ances such as loosening of the clot at certain points. In human 

 pathological material one sees a similar formation of coarse fibrils 

 wherever fibrin in any quantity is deposited as for example, in fibri- 

 nous pleurisy, peritonitis, thrombi, pneumonic exudate, etc. 



Baitsell's interpretation of this change in the fibrin clot as a 

 transformation of fibrin into true fibrous tissue was based on the 

 physical character of the unstained fibres and their reaction to 

 connective tissue stains. Chemical tests were also applied. In 

 their physical character the newly formed fibrils resemble collagen 

 fibrils, but in the opinion of the author and of those to whom the 

 preparations were shown the resemblance is superficial and is 

 certainly not important in a differential study of this kind. 



The stains used by Baitsell were those commonly employed to 

 differentiate connective tissue: Van Gieson's picro-fuchsin, which 

 stains connective tissue red and fibrin yellow, and Mallory's 

 fuchsin-anilin blue with which connective tissue is stained blue 

 and fibrin red. Baitsell obtained negative results with Van 

 Gieson's stain, but with Mallory's stain as modified by Mall 1 the 

 coarse fibrils appeared an ultramarine blue in contrast to a purplish 

 blue of the fine fibrin threads. 2 In my hands this modified stain 



1 Mall, Amer. Jour. Anal., 1901, I, 329. 



2 Baitsell states that both the modified and unmodified Mallory stain was used 

 but his descriptions appear to apply only to the results obtained with the modified 

 stain. 



