140 Mr. C. Creighton on Coagulation-appearances [Jane 15, 



become so excessive that we are no longer at liberty to treat the number 

 of gaseous molecules present in the apparatus as practically infinite and, 

 according to Professor Clerk Maxwell's theory, the mean length of path 

 of the molecules between their collisions is no longer very small com- 

 pared with the dimensions of the apparatus. 



The degree of exhaustion at which an induction-current will not pass 

 is far below the extreme exhaustions at which the logarithmic decrement 

 falls rapidly. 



The force of radiation does not act suddenly, but takes an appreciable 

 time to attain its maximum — thus proving, as Prof. Stokes has pointed 

 out, that the force is not due to radiation directhj but indirectly. 



In a radiometer exhausted to a very high degree of sensitiveness, the 

 viscosity of the residual gas is almost as great as if it were at the atmo- 

 spheric pressure. 



With other gases than air the phenomena are different in degree, 

 although similar in kind — aqueous vapour, for instance, retarding the 

 force of repulsion to a great extent, and carbonic acid acting in a similar 

 though less degree. 



The evidence afforded by the experiments of which this is a brief 

 abstract is to my mind so strong as almost to amount to conviction that the 

 repulsion resulting from radiation is due to an action of thermometric 

 heat between the surface of the moving body and the case of the instru- 

 ment, through the intervention of the residua.1 gas. This explanation of 

 its action is in accordance with recent speculations as to the ultimate 

 constitution of matter and the d}Tiamical theory of gases. 



XI. ^^Note on certain unusual Coagulation- appearances found in 

 Mucus and other Albuminoid Fluids.-'^ By Charles Creigh- 

 T0N_, M.B., M.A. Communicated by Prof. Huxley, Sec. R.S. 

 Received June 9, 1876. 



The following observations were made in the course of re-examining 

 a number of microscopic preparations that had been originally made for 

 other purposes. They relate to certain unusual coagulation-forms that 

 mucous or colloid or other albuminoid fluids assume when they are 

 treated in a particular way. 



In an early investigation of Yirchow's ('Ueber die Form des geronneuen 

 Faserstoffs ') the production of the fibrinous threads of a coagulum was 

 attributed to the contraction of the clot towards particular points, and 

 was compared to the process of crystallization. " We may consider," 

 says Yirchow, " this process to be a kind of organic crystcdlization, wherein 

 each separate fibril must be viewed as a complex of smaller crystalline 

 particles. As in crystallization, so likewise in this case the separate 

 molecules arrange themselves in particular directions to form delicate 



