File:Advanced lessons in practical physiology for students of medicine (1920) (17938826311).jpg

Title: Advanced lessons in practical physiology for students of medicine
Identifier: advancedlessonsi00burt (find matches)
Year: 1920 (1920s)
Authors: Burton-Opitz, Russell, b. 1875
Subjects: Physiology
Publisher: Philadelphia, London, W. B. Saunders Company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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54 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY \NTiting lever. Allow it to register at intervals of two seconds. Allow the drum to revolve very slowly and observe whether the muscle records spontaneous contractions. Draw the abscissa, and adjust the writing lever properly in this line. Start at the beginning of the paper and stimulate the muscle with a single break shock. If the preparation does not react to this strength of stimulus, put in two or more shocks in quick succession—makes and breaks, if j'ou choose. Note the unusual length of the latent period. Allow the muscle to relax fully, which, if the contraction possesses a height of about 5 cm., may require the entii'e length of the paper. Produce a summation of contractions by stimulating the muscle first by means of a make shock and again with a break shock very shortly after it has entered upon its period of relaxation. Naturally, if single stimuh do not prove effective, employ a number of them in quick suc- cession. Employ a brief tetanic current, being careful not to contract the muscle excessively, otherwise it might not be able to complete its period
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Fig. 33.—Contraction of Smooth Muscle (Cat's Bladder). L, Latent period; C, period of contraction; R, period of relaxation; time in seconds. of relaxation before the end of the paper has been reached. Does the character of the "tetanic" curve of smooth muscle differ from that of the curve obtained with single stimuli? Annotation.—Preparations of smooth muscle may be obtained most conveni- ently from the stomach of the frog and the stomach, intestine, and bladder of the cat. No doubt, the bladder is best adapted for this purpose. Having opened the abdomen in deep narcosis, the bladder is partially emptied and lifted out of the wound. A long silk thread is then tied around the urethra at a distance of 1 to 2 cm. from the cervLx of the bladder. The upper pole of the fundus is securely fastened to a pair of needle electrodes and quickly placed in the moist chamber prepared as described above. The silk thread is attached to the writing lever placed at a convenient distance below the floor of the chamber. Do not injure the organ mechanically, and moisten it from time to time with slightly warmed saline solution. If the stomach is employed, cut a ring about 1 cm. in width from its pyloric portion and fasten it in this position to the rod of the moist chamber. To its upper pole attach one of the ^^^res from the secondary coil of the inductorium. To its lower pole attach the wTiting lever by means of a thread and also the other wire from the secondary coil. The same procedure is to be followed in the case of seg- ments of intestine. Be sure not to arrange them horizontally, because only \he circular mu.sde-fibers will give a marked movement of the lever. Under proper conditions of experimentation the frog's stomach will yield contractions 2 to 3 cm. in height.

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