Experimental partial hepatectomy was performed on 10 hcal thy dogs. Re ection of about 60 per cent of tha liver was made. The anima's withstood well the operation and showed no serious post-operative complications. Blood samples were collected for analysis before and after the operation for 50 days. 11 The mean value of fasting blood sugar before the operation was 101.6 +1.69 mg %. A highly significant decrease was observed on the 4th and 8th dys after the operation. The pre-operative total serum pro.eins averaged 7.72 + 0 12 mg%. A significant dcrease was observed on the 4th day after ope'ation till the 15th day. A gradual increase was seen after one month from the operation. Tota! serum cho'este ol averaged 214.3 + 16.64 mg%. There was a prominent decrease four days after the operation. After 30 days of the operation it returned to its original value and re mained rearly so with slight fluctuaticns for about 20 days. The prothrombin time in normal dogs was 9.4 + 0.2 sec. Delay in this time was noted on the 4th, 8th and 15th days af er the operation. The time retuined to normal on the 30th day after the operation and remained so with slight variations for 20 days. All the estimated blood constituents regained their physiologi cal levels after the 50th day of the experiment.