Ride out in hot, humid conditions long enough without rest or proper fluid intake and heat exhaustion can set in; your buddy will be pale, lethargic, sweating profusely, cramping up, nauseous, etc. Get him into the shade, get him cool (use a wet cloth or ice pack), hide the nurse and slowly give him some water to drink. Heat stroke-wherein the temperature-regulation center of the brain stops working and you begin to fry in your own juices-is much more serious. Sweating stops, the skin becomes hot and dry, and the victim may even collapse and fall into a coma. In this case, you need to cool your buddy down by any means possible, and be prepared for mouth-to-mouth resuscitation should he stop breathing. By now, taking water by the mouth won't help enough-the victim will have to be rehydrated by intravenous fluids in a hospital.