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In all vertebrates, as the embryo develops at one pole of the egg, it sinks inwards till it becomes completely enclosed in a hood or sac filled with fluid, the amnion. When the sac or true amnion has completely closed over the embryo, it becomes separated from the outer layer, which remains in contact with the covering of the egg as the false or chorionic amnion.

1. Idiopathic tetany and the various theories as regards its etiology are considered. 2. The previous work upon experimental tetany is dealt with in the three periods— (a) before the recognition of the possible significance of the parathyroid; (b) while the distinction between the thyroids and parathyroids was still doubtful; (c) after the direct implication of the parathyroids in the production of the symptoms had been established. The evidence that the condition is a true tetania parathyreopriva is considered to be conclusive. 3. The method of removing the parathyroids is considered, and the impossibility of getting rid of the internal parathyroids with certainty by any operation but complete thyroparathyroidectomy is indicated. The existence of supplementary parathyroid tissue in about 50 per cent. of cats and in probably about 5 per cent. of dogs is shown to explain the absence of symptoms in some cases of thyroparathyroidectomy. 4. The symptoms of tetania parathyreopriva are considered under the following heads:— I. Their protean character. V. Tremors and fibrillar tremblings. II. Depression. VI. Jerkings. III. Emaciation. VII. Convulsions. IV. Spasticity. VIII. Disturbances of balance. 5. Some of the factors modifying the character and onset of the symptoms are briefly considered:— (a) The nature of the food. (c) Rickets. (b) Age. (d) Pregnancy and lactation.

SINCE Liebig in 1842 developed his famous theory of the source of muscular energy, the influence of muscular work on the metabolism has arrested the attention of many physiologists, and much has been recorded on the subject. From previous observations, we now know that while the principal source of energy is in the non-nitrogenous constituents of the body, the nitrogenous constituents are always decomposed to a greater or less extent if the work is at all excessive. The object of the present research is to attempt to elucidate the source of the proteid material decomposed after muscular work, and generally reinvestigate the subject. The excretion of uric acid and allied nitrogenous bodies and of phosphoric acid received special attention, for an indication of the source of the proteid decomposed may be found in the influence of muscular work on these excretions.Muscular tissue is rich in the native proteid, e.g. globulin, but is poor in nucleo proteids, and consequently, were it found that the increased excretion of nitrogen were accompanied by increased excretion of uric acid and allied bodies, along with an increased excretion of phosphoric acid, substances derived from the decomposition of the nuclein element of nucleo proteids, it would indicate that not muscle but some other tissue supplied the proteid. It is an established fact that in hunger the proteid of one tissue can be called on to supply the wants of another2, and it is of interest to know whether such an