18 MANUAL OF HISTOLOGY. 



digestion into what are termed peptones i.e., easily diffusible substances 

 of very similar or identical constitution. These peptones are by no 

 means so easily precipitated by reagents as the colloid albuminates. 

 Thus, in contradistinction to the latter, they are not thrown down by 

 boiling, by dilute mineral acids, or by acetic acid. On being precipi- 

 tated by alcohol, they may be again dissolved by watery spirits of wine. 

 A polarised ray of light is deflected by them strongly to the left. 



Matters containing collagen and chondrigen, and also mucus, the con- 

 sideration of which will soon occupy us, yield with greater or less certainty 

 corresponding peptones. 



Ferments. 



It has been already noticed above (p. 1 4), that the instability of the 

 albuminates permits of their ready conversion into what are termed 

 ferments. By the action of such substances, we believe them at present 

 to spring in all probability from this source ; the albuminous matters are 

 converted into peptones. The ferments appear combined with water as 

 constituents of the gastric, intestinal, and pancreatic secretions. Others 

 of them, from the mouth and salivary glands, transform amylon, dextrin, 

 and glycogen into grape sugar. A ferment in the pancreatic juice splits up 

 the neutral fats into fatty acids and glycerin. Decomposing albuminous 

 substances convert urea into carbonic acid and ammonia, &c. Thus the 

 mutation of the most important substances in the body introduces a 

 great chemical action in the same, and leads even to the assimilation of 

 new albuminoids in the most extraordinary manner. 



B. Hsemoglobulin. 



13. 

 Hsemoglobulin, Haematoglobulin, Hsematocrystallin. 



We have been recently made acquainted with a remarkable substance 

 of still more complex constitution than the albuminates, which may very 

 easily be resolved into an albuminous matter resembling globulin and 

 into hcematin. 



From the red blood-cells of man and the vertebrates generally, a 

 coloured crystalline substance may be obtained, namely, after destruction 

 of the cells, containing iron, and of the greatest instability. Of this the 

 blood-crystals so long known are composed (fig. 1). From the investiga- 

 tions of the Germans Funke, Lehmann, Kunde, Teiclimann, Bojanoicsky, 

 Rolletl, Hoppe, Bottcher, and others, we learn that the substance which 

 thus crystallizes is by no means the same in all classes of vertebrates, but 

 offers many differences for our consideration as regards solubility and 

 crystalline form. The difficulties of dealing with it chemically are greatly 

 enhanced by its liability to decomposition, and its admixture with other 

 matters. 



It may be obtained with greater or less ease in various ways : by first 

 conducting a stream of oxygen through a mixture of blood and water, 

 and then carbonic acid ; then by evaporation of diluted blood, to which 

 alcohol and ether have been added upon the glass slide of the microscope. 

 Its separation is favoured by the presence of light according to the 

 general opinion. Crystals may likewise be obtained by the freezing and 



