COLD AND HEAT 677 



blood to the head, and a linen sheet, wet in water, of from 

 50° to 80° F., is placed over the animal, the surface beinj^ 

 rubbed, while dashing on the sheet water at the temperature 

 of 50° to 60° F. This process is continued for fifteen or 

 twenty minutes, unless rigor is induced. The method is 

 valuable in the treatment of fever and insolation. The gen- 

 eral rationale is the same as in the case of ablutions, but the 

 antipyretic effect is more marked and permanent. The sheet 

 may be covered, while wet, by blankets, and converted into 

 a wet pack. 



The Wet Pack is applicable for general or local use, and 

 for various purposes. A linen sheet is dipped in water at a 

 temperature of 50° to 70° F., and wrung out very thoroughly. 

 A cold application is put on the head and the sheet applied 

 and covered with dry woolen blankets. The duration of 

 application is from one quarter to three hours, according to 

 the object in view. If it is used as a strictly antipyretic 

 measure, it should be changed frequently. The wet pack 

 differs materially from other hydriatic procedures in that 

 reaction occurs slowly, for there is no artificial stimulus in 

 the shape of friction to accelerate it. The primary contrac- 

 tion of the vessels is succeeded by partial dilatation of them, 

 when the blood from the interior of the over-heated body is 

 cooled on the surface by contact with the sheet and by 

 vaporization of the water. Vascular contraction again occurs 

 owing to the cooling, forcing the chilled blood inward. So 

 there is continual interchange of cooled and heated blood, 

 until the sheet has become thoroughly warmed. After the 

 wet pack is removed, the skin should be dried and the 

 patient well blanketed. 



The interchange of tlood is useful in relieving conges- 

 tion of the internal organs, in aiding nutrition by bringing 

 to the periphery nutriment absorbed from the gastro-intes- 

 tinal tract, and for its tonic effect on the nervous system. In 

 fever, it abates cerebral hyperaemia, delirium and excite- 

 ment, and promotes rest and quiet. 



The Priessmfz Poultice is similar to the wet pack, but a 



