TISSUES OF THE BODY. 117 



all the most important substances in the system, with which we were 

 made acquainted in a former part of the work, are represented in the 

 blood. Many gaps, however, still exist in our knowledge on this parti- 

 cular branch of physiology, owing to the difficulty of the subject. 



The matters which may at present be looked upon with more or less 

 certainty as constituents of the blood are the following : 1. From the 

 albuminous group haemoglobin, albumen, the two constituents of fibrin, 

 namely, fibrinogen and fibrinoplastin, near to which we place globulin, 

 obtained by the splitting up of the latter. Casein is not found, nor are 

 the glutinous substances or elastic matters. 2. Of the solid fatty acids 

 (usually saponified, more rarely as neutral fats), stearic, palmitic (and 

 margaric ?) acids, to which oleic may be added. Of the volatile fatty acids, 

 we find butyric, with lecithin and cerebrin from the brain. 3. Of the 

 carbohydrates, grape sugar, whilst sugar of milk and inosite are missed. 

 4. Of non- nitrogenous and nitrogenous acids, we find lactic and suc- 

 cinic (?), whilst others, as, for instance, oxalic, benzoic, and gallic acids, 

 are absent. 5. Of amides, amido acids, and bases, urea, kreatin (?), krea- 

 tinin (?), hypoxanthin (?), and xanthin (?) ; whilst, on the other hand, 

 other allied matters, as leucin, tyrosin, glycin, taurin, are not contained in 

 it. 6. Of extractives ; and finally, 7, numerous mineral constituents, 

 among which we find, beside water of bases, lime, magnesia, potash, 

 soda; and of metals, iron, copper, manganese (?) ; of acids, carbonic, phos- 

 phoric, sulphuric, hydrochloric, and silicic ; and finally, of gases, carbonic 

 acid, oxygen, and nitrogen. 



A chemical analysis of this kind of the whole mass of the blood, is of 

 but little worth, however ; at most it only adds a few facts to chemical 

 statistics. Such an enumeration of its constituents only renders evident 

 that in it are contained the most important alimentary matters, as well as 

 many of the products of transmutation of our body. 



Owing to the abundance Of elements of composition which it contains, 

 the first and most important point to be made out is 1. What substances 

 enter into the composition of the red corpuscles, and in what proportions 

 do they exist there 1 2. Of what are the colourless cells composed 1 3. 

 Of what materials does the intercellular matter of the blood, the so-called 

 plasma, consist? 4. Since we must expect that some of the ingredients 

 of the blood exist in the cellular elements as well as in the fluid, we ought 

 to determine in what relative proportions they appear in the cells and in 

 the plasma. 



In this way alone could we gain anything like a satisfactory insight 

 into the chemical constitution and physiological properties of the blood, 

 or ascertain what the blood-cell chemically is, and of what nature the 

 fluid is in which it is suspended, and with which it is constantly engaged 

 in interchange of material. 



Do we now ask how far the requirements just stated are to be looked 

 upon as met by the present state of science, we must bear the following 

 points in mind. : Firstly, all efforts to isolate the white from the red cor- 

 puscles of the blood have been hitherto unsuccessful. We are completely 

 in the dark, therefore, as to the composition of the former, and can never, 

 on the other hand, obtain the red perfectly free from the presence of 

 the colourless elements, a source of error which is, however, but incon- 

 siderable in analysing human blood, owing to the small number of the 

 latter contained in it. Then, again, it is only occasionally possible to 

 make an analysis, which is then but approximate, of the blood-cells in 



