54 PHYSICAL CHEMISTRY IN MEDICINE. 



observations are utilized which are noticed when delicate 

 gelatine threads that have been kept in absolute alcohol 

 or have been dried in the air are subjected to the effects 

 of tension or pressure. If such threads are stretched or 

 bent, microscopic examination reveals a cross-striation 

 upon their surface corresponding with parts of the 

 threads that have become white and opaque. The cen- 

 tral portion of the threads may retain its hyaline char- 

 acter. That we are dealing in this case with more or 

 less well-marked breaks in continuity is without question 

 when the manner of their production is considered. 

 BUTSCHLI explains the regularity of the pictures which 

 are produced by saying that the chambers of the stretched 

 honeycomb structure of the gelatine give rise to a system 

 of stripes which cross each other diagonally, just as is 

 the case with a net when this is pulled in certain direc- 

 tions. It would be an argument in favor of this explana- 

 tion if it could be shown that in gelatine threads which 

 had previously not been treated with fixing-agents the 

 distance between the stripes is less than the diameter of 

 one of the honeycomb chambers. This is, however, not 

 the case. In a large number of measurements BUTSCHLI 

 has determined the diameter of the latter to be 0.7 /* in 

 gelatine that has been treated with chromic acid or 

 alcohol, while the distance between the stripes in untreated 

 gelatine threads is 2.1 to 2.3 //. That the honeycomb 

 structure of gelatine threads which have been treated 

 with precipitating agents is more or less cross-striated 

 cannot seem strange when the systems of cross-striation 

 are looked upon as expressions of a definite distribution 

 of tension and pressure in the threads. As has already 

 been described above, such stresses may impress them- 



