308 THE BLOOD. 



anilin, hydrocyanic acid, nitrobenzol, etc., it is of a brownish-red or 

 a chocolate color. These changes are, as we shall presently see, due 

 to certain chemical compounds of haemoglobin which are not nor- 

 mally found in the blood. In leukaemia, in which a most remark- 

 able increase in the leucocytes may occur, the blood at times pre- 

 sents a milky appearance. This is not referable to any change of 

 the normal coloring-matter, however, but to increase of the leucocytes 

 as such. 



The Odor. The odor of the blood is characteristic, but is different 

 in different species of animals. It can be intensified by treating the 

 blood with a small amount of fairly concentrated sulphuric acid. In 

 part it is owing to the presence of odorous salts of certain fatty 

 acids, and to a slight degree also to trimethylamin. Other sub- 

 stances, however, are also concerned in its production, but of their 

 nature nothing is known. 



The taste of blood is salty, but at the same time insipid. It is 

 referable, no doubt, to the mineral constituents of the plasma. 



The Specific Gravity. The specific gravity of normal blood 

 seems to vary with the amount of hemoglobin. It is influenced 

 by the age and sex of the individual, the process of digestion, the 

 amount of exercise taken, pregnancy, etc. It is dependent, more- 

 over, upon the bloodvessel from which it is drawn, and differs 

 somewhat in different animals. Generally speaking, it varies in 

 healthy adults between 1.058 and 1.062. It is higher, as a rule, in 

 men (1.059) than in women (1.065) and in children (1.050-1.052). 

 Under pathological conditions the variations are much greater. It 

 may thus fall to 1.025 and rise to 1.068. It is to be noted, more- 

 over, that the specific gravity does not necessarily vary with the 

 amount of haemoglobin, and in nephritis, various circulatory dis- 

 turbances, in leukemia, and in the anaemias following profuse hem- 

 orrhages or inanition, care should be had not to draw inferences 

 as to the amount of blood coloring-matter from a determination of 

 the specific gravity. 



Determination of the Specific Gravity. Hammer schlag's 

 Method. A cylinder measuring about 10 cm. in height is partly 

 filled with a mixture of benzol (sp. gr. 0.889) and chloroform 

 (sp. gr. 1.526), so that the specific gravity lies between 1.050 

 and 1.060. Into this solution a drop of blood is allowed to 

 fall directly from the finger, care being taken that it does not 

 come in contact with the walls of the vessel. The drop, moreover, 

 should not be too large, as it will otherwise separate into several 

 droplets, and thus give rise to inaccurate results. It is then brought 

 to suspension in the middle of the fluid, by adding a little chloro- 

 form or ether, according to its tendency to sink to the bottom or to 

 rise to the surface. As soon as it remains in the middle the mixture 

 is filtered through a layer of linen, and its specific gravity deter- 

 mined by means of an accurate hydrometer, which is graduated to 

 the fourth decimal. The figure obtained represents the specific 



