The systemic arterial blood pressure response of the dog to injection of Escherichia coli endotoxin is characterized by a sudden precipitous drop, a partial recovery and a subsequent slower decline over a period of hours. Utilizing a device for quantitatively estimating changes in weight of organs in vivo, an increase in liver weight of from 80 to 350 g was noted within 1-2 minutes following injection of E. coli endotoxin. A simultaneous increase in weight of small intestine of lesser magnitude (28-170) was noted at the same time and is believed due to back pressure from the liver. Whereas the liver returns to normal weight within 5-25 minutes the small intestine continues to increase in weight reaching a maximum of from 196-770 g approximately 1 hour following endotoxin injection.