Page:Proceedings of the Royal Society of London Vol 69.djvu/204

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The present investigation has included a very large number of ex- periments, performed at different times during the last 10 years, the blood-vessels of the ox, horse, and sheep being the ones chiefly examined. The conclusions arrived at apply to the vessels of healthy animals.

Post-mmieni Contraction. The occurrence of post-mortem contraction in the arteries is described, and its exciting causes (mechanical stimula- tion, exposure to air, cooling, &c.) stated, and the remarkable per- sistence of this contraction over many days in the case of the horse's carotid kept in olive oil over a fortnight, &c.

The influence of chloroform vapour and saline decoction of supra- renal medulla in causing or increasing contraction are described. Also the method of preventing the occurrence of post-mortem contraction by freezing, and various methods of removing contraction when it has once been established, by potassium sulphocyanide, ammonia vapour, heating to 50 55 C., keeping at 38 40 C. for 24 hours, &c., or merely keeping at room temperature (in blood) for a number of days. The different effects of sulphocyanide on arterial muscle and on skeletal muscle are illustrated.

Very different measurements (as to lumen, thickness of wall, &c.) are obtained from the same artery in contraction and in relaxation.

Effects of Changes in Temperature. The effects of changes of tempera- ture have been studied in various ways by causing strips (transverse and longitudinal) of the vascular wall to act upon recording levers (supported by long, feeble, spiral springs) while the strips were heated in an oil-bath, &c.

Relaxed arteries give results very different from contracted arteries, and generally similar to veins the chief feature on heating being a very marked shortening at 60 65 C.

Contracted arteries show a definite series of changes when the tem- perature is raised. Up till two or three days after death there are usually the following changes : Shortening between 25 and 35, lengthening about 40, shortening at 45 50, extensive lengthening at 50" 55, iVc., shortening at 60 65 ; a certain amount of lengthen- ing occurs during subsequent cooling.

When the artery is kept longer these changes show a definite order of disappearance ; while any contraction remains there is always relaxation at 50" 55, while at a later stage, when contraction is