488 APPENDIX. 



remarkable properties which Reichert noticed in the crystals on 

 which he made his observations. Thus, for instance, they swell in 

 dilute acetic acid, so that their diameters are increased three or 

 four-fold ; but they recover their former volume when washed, or 

 when the acid is neutralised. They must, therefore, be secondary 

 crystals, formed from the coagulation of the originally soluble 

 crystallised substance. 



Composition, The discovery of a crystallisable protein-sub- 

 stance appeared at once to afford a new means for obtaining more 

 secure points of support for the establishment of its true consti- 

 tution ; but hitherto the elementary analyses of this substance 

 have not furnished the desired information, on the one hand, 

 because the results obtained were too nearly identical with those 

 yielded by the other protein-bodies, and on the other hand, 

 because no guarantee of the perfect purity of the substance could 

 be obtained. We must defer to a future page the consideration of 

 the reasons which lead us to reject the validity of the results of 

 former elementary analyses, and we will here only observe, that 

 the membranes of the coloured blood-corpuscles and the coloured 

 blood-cells penetrate through all filters and follow the blood- 

 crystals, so that only a tolerably pure, and not an absolutely pure 

 crystalline substance, can be obtained. In the mean while, we 

 may at least hope to obtain a somewhat more definite insight into 

 the constitution of this substance through its products of decom- 

 position than we can possibly hope to attain in the case of the 

 other protein-bodies. We have already mentioned that the dif- 

 ferent forms of the crystals of certain kinds of blood clearly show 

 that the substances we have here to consider are homologous 

 bodies, whose comparative analyses promise to afford at least some 

 information regarding the constitution of these mysterious sub- 

 stances. 



I have hitherto only analysed this substance from the blood of 

 guinea-pigs, and hence I cannot venture to found any conclusion 

 on such analyses ; both tetrahedric crystals and the prismatic 

 (those of the dog) are very poor in ash-constituents : I found that 

 both kinds contained about !- of mineral substances, the princi- 

 pal part of which consisted of oxide of iron, which frequently 

 amounted to 72J of the ash ; about 21-g of the ash was phosphoric 

 acid, while there was, moreover, a little lime and potash. This 

 substance contained much less sulphur than is found in any other 

 protein-substance. 



As these crystals are always coloured, the question here sug- 



