444 DOCTRINE OF MUSCULAR CONTRACTION. 



Experiments servations of Dr. Dowler, of New Orleans, on the automatic 

 of Dr. Dowler. movements that sometimes take place after death by yellow 

 fever. After respiration had ceased, each hand in succession was car- 

 ried to the throat, and then to the crown of the head, and so back again 

 to the breast. In another instance, on being stimulated by a blow, the 

 arm was extended upward, and the hand could even be made to slap the 

 mouth ; or when the leg hung down, if the flexors of the hamstring were 

 struck, the heel was drawn upward. These manifestations continued 

 for between three and four hours, and even occurred in amputated limbs. 



Contractility lasts for a different period, not only in different animals, 

 Duration of but even in different parts of the same animal. Thus, in man, 

 contractility, ft declines in the following order: in the left ventricle first, 

 then in the intestines and stomach, the urinary bladder, right ventricle, 

 oesophagus, iris, in the voluntary muscles of the trunk, lower and upper 

 extremities, and, finally, in the left and right auricle of the heart. 



Assuming that the diameter of each muscular fibre is, on an average, 

 Distance at the 10 Q 00 of an inch, and that each fasciculus is the -^ of 

 which a muscle an inch, it may be inferred that each fasciculus contains about 

 enced by^a U 650 fibres. Now, since the nerves do not penetrate the sar- 

 nerve. colemma, the influence which they exhibit must be efficacious 



at a distance; and if we take the maximum measurements which have 

 been made of muscular fasciculus, we may safely conclude that that in- 

 fluence extends at least through a distance of -^J-g- part of an inch. 



It is not necessary for us, in this place, to enter on a discussion of the 

 T functions of nerve fibres, whether they exert a magnetic 



that muscular agency, or act by rise of temperature, or, from an abrupt po- 

 suHsTronimus- ^ ar termmat i n deprived of its white substance of Schwann 

 cuiar disinte- permit the escape of their current into the muscle fibril, and 

 thence into the corresponding denuded pole of a centripetal 

 nerve beyond, the current being determined through the muscle by rea- 

 son of the better conducting power of that structure. The immediate 

 cause of muscular contraction is to be sought for in the muscles them- 

 selves, and this, I think, is much more obvious than is generally sup- 

 posed. So far from there being any thing mysterious or incomprehen- 

 sible about it, as some writers insist, we probably shall not be very far 

 from the truth if we assert that muscular contraction is the necessary 

 physical result of muscular disintegration, and without here consider- 

 ing the various ways by which that muscular disintegration may be 

 brought about, such is the doctrine that I now present. 



Reviewing the various conditions under which contraction occurs, I re- 



Change in mus- S ar( ^ destructive metamorphosis as the primary and leading 



cie after con- one. Every thing seems to indicate that the contraction of 



a fibril can not take place without the loss of a part of its 



