Respecting the organisation of this worm I may observe that the mature joints have a more complicated uterine organ than obtains in _Tænia solium_, presenting nearly double the number of lateral branches. They are more closely packed, running outwardly in an almost parallel manner. The first sexually mature proglottis occurs at about the 450th joint, but whereas, in the pork tapeworm, only some 200 subsequent segments share this perfect character in the beef tapeworm, according to Leuckart, as many as 360 or even 400 mature joint may be present. The joints are very liable to form monstrosities; these abnormalities sometimes affecting the reproductive organs, which become doubled or even trebled. In the Hunterian collection there is a proglottid showing twenty-two sexual orifices. Dr Cullingworth, of Manchester, has described a specimen in which the joints are curiously tripartite. As already hinted the true source of this parasite has been proved by experiment; the first successful worm-feeding having been accomplished by Leuckart. Mosler’s, and subsequently my own feeding experiments, immediately followed. Other successful experiments with this species have been conducted by Zurn, Probstmayer, St Cyr, Perroncito, Masse and Pourquier, and Zenker. As will be again mentioned below Dr Oliver, R.A., whilst stationed at Jullundur, successfully reared the adult tapeworm in a Mohammedan groom and in a Hindoo boy. It will also be seen that Prof. Perroncito reared the worm in a student in fifty-four days. In my own experiments on animals I was assisted by Professor Simonds. The feeding materials were tapeworms expelled from my own patients. We obtained the following interesting results: _Exp. 1._--A calf. First feeding, Dec. 21st, 1864. Marked symptoms. Slaughtered April 3rd, 1865. Result positive. _Exp. 2._--A calf. First feeding, April 13th, 1865. Second, third, and fourth feedings in May and June. No symptoms. Died on Sept. 3rd, 1865, after thirty-six hours’ illness with “cattle plague.” Result stated to have been negative as far as the muscles were concerned. Viscera not examined. _Exp. 3._--A Dutch heifer. First feeding, March 3rd, 1865. Three subsequent feedings. Symptoms only slight. Slaughtered April 4th, 1866. Result positive. Measles especially numerous in the diaphragm, but all had undergone calcareous degeneration. _Exp. 4._--A calf. Fed May 27th, 1872, with ripe proglottides. Marked symptoms set in on June 7th, which began to abate on the 12th, and had nearly disappeared by the 20th of the same month. The record of the post-mortem result has been lost; but the animal was infected. _Exp. 5._--A calf, which had been made the subject of a “glanders experiment.” First fed on Oct. 17th, 1872, and thrice in the following year, Jan. 1st and 11th, and March 8th. No symptoms having appeared the animal was kept for six or eight months after the last feeding. Seeming to be free from disease of any kind, it was sold as a sound heifer.