24 THE METHOD OF MAKING POST-MORTEM EXAMINATIONS. 



The condition of the aortic valves and of the endocardium, and the 

 thickness and appearance of the walls of the left ventricle, papillary 

 muscles, chordae tendiuese, etc., are now noticed. The right ventricle is 

 now opened by an incision through its anterior wall, close to the septum, 

 and examined in the same way. We sometimes see the endocardium of 

 the upper part of the left ventricle thick and white, without the exist- 

 ence of valvular lesions or any clinical history of disease. The endocar- 

 dium and valves are often stained red, particularly in warm weather, by 

 imbibition of coloring matter of the blood, set free by decomposition. 

 To complete the examination of the cavities the enterotome is passed into 

 each auricle, carried down into the corresponding ventricle, and an 

 incision made along the outer border of both auricle and ventricle to the 

 apex of the latter. In this way the auriculo-ventricular valves are com- 

 pletely exposed. The coronary arteries should be opened through all 

 their main trunks, with fine probe-pointed scissors, and carefully 

 examined for marks of inflammation, emboli, thrombi, etc. 



After removing the blood the heart should be finally weighed. The 

 normal average weight of the heart in adults is, according to an estimate 

 of H. D. Arnold, 1 in males about 290 grams; in females about 260 

 grams. 



The weight of the heart relative to that of the body is in males about 

 1 : 158 to 178 ; in females, about 1 : 149 to 176. According to Buhl, the 

 average thickness of the wall of the left ventricle at about the middle of 

 the cavity is from 1.6 cm. to 1,7 cm. ; of the right ventricle, from 0.4 to 

 0.6 cm. 



Generally speaking, the size of the heart corresponds to the size and 

 the development of the individual. In judging of an increase or de- 

 crease in its size we must consider the weight of the organ and the thick- 

 ness, of its walls. If the person die while the heart is contracted, the 

 walls of the ventricles will appear thicker, their cavities smaller than 

 usual. If he die of some exhausting disease like typhoid fever, or if 

 decomposition have commenced, the heart walls will usually be flabby 

 and the cavities will appear larger than usual. 



PRESERVATION OF SPECIMENS. Parenchymatous and fatty degeneration of the heart 

 may be studied microscopically by teasing the fresh muscle in one-half-per-cent salt 

 solution, or by examining in the same solution fresh sections made with the freezing 

 microtome, or by hardening small pieces of the muscle in one-per-cent osmic acid and 

 teasing in equal parts of glycerin and water. 



The heart valves may be stretched on a flat cork with pins and hardened in Orth's 

 or Zenker's fluid or alcohol. For the methods of detecting bacteria in ulcerative endo- 

 carditis, see section on Staining Bacteria. When the presence of bacteria is suspected, 

 cultures should be made and the tissues should be preserved in strong alcohol. 



The Pleura! Cavities are next examined. The hand is passed into 

 each, and the existence of serous or fibrinous exudation or of old adhe- 

 sions ascertained. The method of detecting the presence of air has been 



1 Arnold, " Observations on the Weight of the Normal Heart in Adults, in Two 

 88 Sixteen Cases." Reports of the Boston City Hospital, tenth series, 1899, 



