Colic persists with great intensity for ten to twelve hours, interrupted only by rare periods of calm. At the end of this time, however, it may suddenly disappear, and the animal may fall into a semi-comatose state. This indicates the onset of necrosis in the invaginated section, the painful reflexes no longer being transmitted to the sympathetic system. The disappearance of colic is sometimes regarded as a sign of improvement, but this improvement is illusory. From this time onwards the animals stand stolidly, obstinately refusing both food and drink. If they lie down, it is with great care. Palpation of the right side of the abdomen is painful, and the animal actively resents it. One of the most important and constant signs at this stage is the absence of defæcation, due to obstruction of the intestine, which is occluded. The animals may survive for ten, twelve, or even fifteen days (see also Möller and Dollar’s “Regional Surgery,” _loc. cit._). The invaginated, necrosed portion may even be passed with the fæces, and recovery may occur, the continuity of the intestinal tube being secured by the adhesion of the serous surfaces; but such spontaneous recoveries are exceptional. Usually after a few days death results from peritonitis. Occasionally, trifling invaginations may become reduced spontaneously, Diarrhœa, with the passage of blood-stained material is then seen for a time, a sign which alone at this stage would justify the diagnosis of invagination. =Diagnosis.= The intensity of the colic and the absence of defæcation for several days afterwards, justifies the diagnosis of invagination. Purgatives then remain without effect. In addition, rectal exploration offers a valuable means of diagnosis. The last portions of the intestine are found absolutely empty, and the arm when withdrawn is found to be covered with viscous blood-stained mucus, resulting from the sero-sanguinolent exudate, due to compression of the blood-vessels. In cases of this kind accompanied by the above-mentioned symptoms abdominal exploration by the rectum should always be practised, but it rarely gives exact information. The hand, when passed towards the right flank, may sometimes reach the invaginated part, which conveys the impression of a cylindrical swelling. The invagination, however, can rarely be reached. If the operator is successful, he will find that as he displaces this cylindrical mass or attempts to grasp it, the animal shows signs of exaggerated sensitiveness. =The prognosis= is of exceptional gravity. Apart from the rare cases where the invaginated portion becomes necrotic and is eliminated, death is inevitable. Unless an operation is performed, septic peritonitis may develop about the fifth or sixth day.