ADDITIONS AND NOTES TO VOL. I. 493 



use of oxygen, and by the mere application of carbonic acid, in 

 obtaining these crystals in sun-light ; but then only in far 

 smaller quantities than in those cases in which the blood had been 

 previously impregnated with oxygen. I discovered, from a series 

 of comprehensive quantitative determinations, the particulars of 

 which I have elsewhere* given, that the crystals are formed with far 

 the greatest rapidity when the oxygen is suffered to pass through 

 the blood in a slow stream for about 15 minutes before the appli- 

 cation of the carbonic acid ; for if carbonic acid be first, and 

 oxygen be subsequently passed through the blood, the latter 

 appears to hinder the process of crystallisation ; but when the 

 fluid is introduced into carbonic acid after it has been im- 

 pregnated with oxygen, the crystallisation begins almost in- 

 stantaneously. This crystallising process appears, moreover, to 

 occur with a rapidity proportional to the length of time that the 

 fluid has been in contact with the oxygen before the application 

 of the carbonic acid. 



Different microscopical observations have appeared to show 

 that the presence of fibrin is inimical to the formation of crystals, 

 and that serum is indispensable to their production, but, as we 

 have already observed, the presence of fibrin exerts no action, 

 either favourable or the reverse, on the crystallisation. The serum is 

 equally devoid of all influence on this process, for crystals, and 

 some very pure ones, may even be obtained from the later 

 rinsings of chopped blood- clots, after they have been stirred and 

 washed three or four times with water, although they certainly 

 cannot retain any great amount of serum. No crystals, bearing 

 even a remote affinity to the above-described blood-crystals, can 

 be obtained from the serum either by these means, or by micro- 

 scopical treatment under glass plates ; hence we are scarcely going 

 too far when we assert that observers who, like Robin, assert that 

 they have procured the true blood-crystals from the serum, are 

 entirely mistaken, and that they would be perfectly correct in 

 regarding such crystals, which were noticed by every careful 

 observer long before the discovery of the true blood-crystals, as 

 mineral salts. 



Although I very reluctantly enter upon the discussion of a 

 subject which is still being made the object of inquiry, and cannot 

 therefore be determined pending such an examination, I. have 

 thought that I could scarcely any longer avoid giving some notice 

 of it. The observations to which I have already referred, together 

 * Ber. d. konigl. saclis. Ges. d. Wiss. zu Leipz. 1853. 



