SECT. 222.] INVESTIGATION OF HEART AND VESSELS. ^5 



that when, from aiw cause, the individual becomes poorer in blood, 

 it may be replaced in a short time, together with its red blood- 

 cells ; but it is quite undetermined whether, under ordinary con- 

 ditions, an energetic solution and rc-formation of blood-cells takes 

 place. Since a formation of blood-globules cannot be definitely 

 observed, we can only hope to bring this question to a decision by 

 seeking for proofs of their solution ; but the observations which we 

 possess on this point arc not of a nature to warrant the inference, 

 that a change of the elements of the blood, is constantly taking- 

 place at short intervals ; for though an enormous number of decom- 

 posing blood-globules may be found in the spleen of many animals, 

 still the frequent and regular return of a process of solution of the 

 blood-corpuscles in this organ has not yet been demonstrated. 

 Taking together all the facts known to us, I believe, then, that the 

 question, when and in what measure the blood-globules of the 

 adult perish and form anew, cannot possibly be determined defi- 

 nitely at present ; yet I am inclined to the opinion, that the 

 elements of the blood are, throughout, less transitory structures 

 than is usually believed. 



The investigation of the heart is easy, as regards the muscular fibres them- 

 selves, and their anastomoses may be detected with facility in any carefully 

 made preparation ; on the other hand, there are great difficulties in tracing 

 the course of the fibres in this organ. Hearts which have been macerated in 

 weak alcohol are best adapted for this purpose, and it has long been recom- 

 mended to employ hearts that have been boiled, either when fresh or after 

 being salted for some weeks. In place of this method, Purkinje and Palicki 

 recommend the heart to be boiled in a solution of common salt, or still better, 

 of sulphide of calcium ; while Ludwig prefers to remove the pericardium, and 

 then to lay the heart in water, repeating the soaking along with a gentle 

 pressure every time that he removes a layer of the muscular fibres. — For the 

 Mood-vessels, previous dissection of them into lamella} with the knife and 

 forceps, however carefully performed, does not suffice ; but their investigation 

 must also be conducted by means of transverse and longitudinal sections of 

 the entire wall of the vessels. Portions of the vessels should be spread out 

 and dried on paper, and then a fine section, even of very thin vessels, may be 

 obtained. Sections thus obtained should be softened in water before exami- 

 nation; they should be treated with acetic acid or with nitric acid of 20 per 

 cent. ( Weyrich), if we desire to study the muscular fibres ; other preparations 

 should be treated with caustic soda, and in these ways, the elastic tissue of 

 the vessels comes out very beautifully. For the rapid demonstration of the 

 epithelium, of the elastic inner coat, and of the muscular coat, by themselves 

 apart from their connections, the large vessels at the base of the brain have 

 shown themselves to me to be best adapted. The elastic membranes of the 

 tunica media can be readily isolated after maceration in acetic acid. The 

 muscular fibres of this coat are always seen on teasing it out, or come into 

 view readily on the addition of nitric acid. — For the study of the capillaries 



