COLD AND HEAT 497 



may induce suppuration. Under this head may be mentioned setons and 

 issues of rowel. A seton is a piece of tape or other material, introduced 

 through an incision in^ the skin and thence under the skin in the con- 

 nective tissue, and finally out through the skin at a short distance from 

 the point of entrance. The loose ends are then knotted together, and 

 the whole loop is drawn through the wound once daily to keep up con- 

 stant irritation and suppuration. An issue of rowel is a piece of gauze 

 or tow, which is passed into an incision, where the substance remains, 

 and causes continual irritation and suppuration. To intensify their irri- 

 tant action, both setons and issues of rowel may be first saturated with 

 cantharides ointment or oil of turpentine. They have been employed in 

 acute disease of the eye, meningitis, "strangles," and in joint and shoulder 

 lameness, near the seat of trouble. Setons and issues of rowel are bar- 

 barous and dirty, and fortunately have become obsolete. 



Cold and Heat 



Cold. — Cold and heat are only relative terms. As lised here, they 

 refer, respectively, to a thermal intensity below or above that of the body. 

 Cold is usually applied by means of water in some form. In veterinary 

 practice we are limited in the employment of cold air, as a medium, to 

 the use of free ventilation and protection of animals from the solar heat.* 

 Cool air is especially desirable in the treatment of most febrile affec- 

 tions by lowering temperature and serving as a stimulus to the respira- 

 tory, circulatory and nervous functions generally. Locally, cold causes 

 contraction of the peripheral vessels and muscles of the skin, forcing out 

 fluids from the part and reducing local temperature. This is more dis- 

 tinctly noticeable in congested areas. If the application is very severe 

 or long continued, the vessels lose their tone, become paralyzed, and we 

 have passive congestion, inflammation, and finally death. 



^ Ordinarily, reaction sets in after the use of cold, more particularly 

 if followed by heat, when an active hyperemia is substituted for the ische- 

 mia. This is brought about both by reflex stimulation of the heart by 

 the cold, and local dilation of the vessels. Therefore, when we wish to 

 constringe parts, we use moderate cold continuously; but, by alternating 

 cold and heat we may accelerate the blood supply, and by first forcing 

 out, and then bringing back the fluids of the tissues, we can maintain 

 such an activity of the circulation that even solid exudations are absorbed. 

 Cold, locally, lessens nervous irritability and pain directly, and, also, by 

 contracting the afferent vessels, it diminishes the impact of the blood on 

 sensitive parts. Moderate heat is said, nevertheless, to produce much 

 the same result by relaxing the capillaries of the collateral circulation, 

 thus draining off the blood and relieving tension in the inflamed part. 

 Tissue change is diminished, locally, by the action of cold. Suppuration 



»The cold air treatment— of lobar pneumonia, especially— is now exceedingly- 

 popular in human medicine. The patients are kept outdoors even m the coldest 

 weather under shelter and well-covered. Reduction of fever and stimulation ot 

 the vital centres are among the chief advantages accruing. The same treatment 

 applies to animals. In pneumonia of horses an abundance of fresh, cold air 

 should be secured with the animal well blanketed and the limbs bandaged. 



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