taining the suboxide in the dissolved state, a reducing substance becomes developed, or else that the amount of oxide of copper appropriated to the oxidation of the sugar becomes altered in the presence of the large amount of potash which it is necessary to employ.

Lastly, it may be observed that a close conformity exists between the figures in columns 4 and 5. The results obtained by the gravimetric method are thus confirmed by the volumetric results obtained by means of the ammoniated form of the cupric test. Seeing that separately prepared specimens of the respective samples of blood were submitted to the two kinds of analysis, the conformity is certainly striking, and gives strong weight to the validity of the results yielded by the gravimetric method.

One of the points referred to in my second communication* is the spontaneous disappearance of sugar from the blood after withdrawal from the body. It is a part of Bernard's doctrine that the natural seat of destruction of sugar within the system is in the systemic capillaries, and if it can be shown that an active disappearance of sugar occurs in the blood after removal from the vessels, support is given to his proposition. I cited the observation which has been adduced by Bernard to illustrate that a marked aptitude exists for the disappearance of sugar under the circumstances named. According to this observation, a reduction from 1.070 to 0.880 parts per 1,000 occurred during the first half-hour, and at the end of 24 hours the analytical result obtained is represented as standing thus-0·000. I stated that my own experience furnished evidence of a widely different nature, and introduced the figures yielded by five observations in proof of this assertion.

The gravimetric process is only suited for the examination of blood before decomposition has set in, as the result would be vitiated by the presence of ammonia as a product of decomposition, the effect being an interference with the deposition of the cuprous oxide. With the ammoniated cupric test, however, any state is suitable; and since my communication of June 21st, 1877, was published, I have applied this process, as well as Bernard's potash process, to blood which has been kept for lengthened periods, instead of limiting the examination, as I had previously done, to the first twenty-four hours. The results obtained were quite unlooked for, and quite irreconcileable with the representation in Bernard's observation, which has been referred to, that at the end of twenty-four hours the blood ceased to give any indication of the presence of sugar.

I have before me a large amount of recorded experience, but need only select a few illustrative examples, for the information supplied is of the same nature throughout. In no case, although the blood had acquired a highly offensive character from putrefaction, has it failed to

* "Proc. Roy. Soc.," vol. xxvi, p. 346.

exercise a decided amount of reducing power over the copper test. It will be seen in the succeeding observations that there is a period during the first few days when the reducing power undergoes a pretty sudden fall, and that it afterwards remains nearly stationary. If the reducing action is to be attributed to sugar, and sugar only, it would have to be said that sugar can exist in a mass of putrefied blood without undergoing destruction. It seems to me, and this view is supported by evidence to be presently adduced derivable from the addition of sugar to decomposing blood, that there is another reducing substance present besides sugar which is not affected in a similar manner by contiguous decomposition. The period of sudden fall, it appears, may be taken. as corresponding with the disappearance of sugar, and this, it will be noticed, presents a variation within certain limits. In the observations at the top of the list the period is more prolonged than in those lower down. It is possible that this may have arisen from the atmosphere of the laboratory having become influenced by the presence of decomposing samples of blood.

The earlier observations were conducted with the application of Bernard's process only, as it was not until June, 1878, that I began to apply the ammoniated cupric liquid. In the employment of this liquid the same product prepared from the blood was used as for Bernard's mode of testing. It is noticeable that the results yielded by the two processes differ from each other in the manner that has been already commented upon.

Decomposition of Blood in relation to Sugar.

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In the following series of experiments sugar was added to blood at different periods after withdrawal. The results furnish the same kind of evidence as that obtained through the previous observations. marked descent is noticeable in the reducing power until a certain point is attained, after which but little change occurs, however long the blood may be kept, and however putrid it may become. It seems, therefore, as already suggested, that there is a reducing agent in the blood which comports itself differently from sugar. If the reducing action were due solely to sugar, it is not intelligible that there should be a more or less sharp descent to a certain point, and then that

the condition should remain comparatively stationary. There is no reason that the last portion of sugar should behave differently from the first. Something having a reducing power, on the other hand, appears to exist which possesses a stability greater than that enjoyed by sugar, and which, thus resisting the influence of the changes of decomposition, produced the reducing effect on the test exerted by the blood after keeping for thirty days.

Observations on the Blood after the addition of Sugar.

In a further series of experiments, blood with added sugar was subjected to the influence of a current of different gases. I was desirous of ascertaining if oxygen promoted the disappearance of sugar, and counterpart observations were made with carbonic acid and hydrogen. The results obtained afford no evidence of any chemical action being exerted. Whatever slight effect occurred, I think, may be assumed to have arisen from increased molecular action excited by the transit of the gas.

Passage of Gases through Blood in relation to the disappearance of