EFFECT OF HEAT, WATER, AND ACIDS ON MUSCLE. 469 



protoplasm of plants and animals, e.g., of the amoeba, is coagulated by heat, giving 

 rise to heat rigor. 



Schmulewitsch found that the longer a muscle had been excised from the body, the greater 

 was the heat required to produce stiffening. Heat-stiffening differs from cadaveric rigidity 

 thus : a 13 per cent, solution of ammonium chloride dissolves out the myosin from a cadaveric 

 rigid muscle, but not from one rendered rigid by heat {Schipiloff). If the rigid cadaveric 

 muscles of a frog be heated, another proteid coagulates at 45, and lastly at 75 the serum- 

 albumin itself. Hence, both processes together make the muscle more rigid ( 295). 



2. When a muscle is saturated with distilled water, it produces " water- 

 stiffening " an acid reaction being developed at the same time. 



Muscles rendered stiff by water still exhibit electromotive phenomena, while muscles 

 rendered rigid by other means do not {Biedermann). If the upper limb of a frog be ligatured, 

 deprived of its skin, and dipped in warm water, it becomes rigid. If the ligature be removed 

 and the circulation re-established, the rigidity may be partially set aside. If there be well- 

 marked rigidity, it can only be set aside by placing the limb in a 10 per cent, solution of com- 

 mon salt, which dissolves the coagulum of myosin (Preyer). 



3. Acids, even C0 2 , rapidly produce "acid-stiffening," which is probably 

 different from ordinary stiffening, as such muscles do not evolve any free C0 2 

 (L. Hermann). The injection of 0*1 to 0*2 per cent, solutions of lactic or hydro- 

 chloric acid into the muscles of a frog produces stiffening at once, which may be 

 set aside by injecting 0*5 per cent, solution of an acid, or by a solution of soda, or 

 by 15 per cent, solution of ammonium chloride. The acids form a compound with 

 myosin (Schipiloff). 



4. Freezing and thawing a part alternately, rapidly produce stiffening ; and it 

 is aided by mechanical injuries. 



Poisons. Rigor mortis is favoured by quinine, caffein, digitalin, [a concentrated solution of 

 caffein or digitalin, applied to the muscle of a frog, produces rigor mortis], veratrin, hydrocyanic 

 acid, ether, chloroform, the oils of mustard, fennel, and aniseed ; direct contact of muscular 

 tissue with potassium sulphocyanide {Bernard, Setschcnoiv), ammonia, alcohol, and metallic salts. 



Position of the Body. The attitude of the body during cadaveric rigidity is generally that 

 occupied at death ; the position of the limbs is the result of the varying tensions of the different 

 muscles. During the occurrence of rigor mortis, a limb, or more frequently the arm and fingers, 

 may move (Sommer). Thus, if stiffening occurs rapidly and firmly in certain groups of muscles, 

 this may produce movements, as is sometimes seen in cholera. If cadaveric rigidity occurs very 

 rapidly, the body may occupy the same position which it did at the moment of death, as some- 

 times happens on the battle-field. In these cases it does not seem that a contracted condition 

 of the muscle passes at once into rigor mortis ; but between these two conditions, according to 

 Briicke, there is always a very short relaxation. 



Muscles which have been plunged into boiling water do not undergo rigor mortis, neither do 

 they become acid {Du Bois-Reymond), nor evolve free C0 2 {L. Hermann). 



Work done during Rigidity. A muscle in the act of becoming stiff will lift a weight, but 

 the height to which it is lifted is greater with small weights, less with heavier weights, than 

 when a living muscle is stimulated with a maximal stimulus. 



Analogy between Contraction and Rigidity. L. Hermann has drawn attention 

 to the analogy which exists between a muscle in a state of contraction and one in 

 a state of cadaveric rigidity both evolve C0 2 and the other acids from the same 

 source ; [both acts take place without the consumption of O]. The form of the 

 contracted and of the stiffened muscles is shorter and thicker; both are denser, less 

 elastic, and evolve heat ; in both cases, the muscular contents behave negatively 

 as regards their electromotive force, in reference to the unaltered, living, resting 

 substance. Hence, he is inclined to regard a mtfscular contraction as a temporary, 

 physiological, rapidly disappearing rigor. Rigor mortis is in a certain sense the 

 last nickering act of a living muscle, [and he regards contraction as partial 

 death of a muscle. But this is no explanation, and moreover there are important 

 points of difference. We have no proof of a coagulum being formed during con- 

 traction, while the extensibility is increased during contraction and much diminished 

 during rigor.] 



Disappearance of Rigidity. When rigor mortis passes off, there is a consider- 



