Others, like Bechhold, maintain that the urates are present in the blood in a _colloidal_ form, impossible of excretion by the kidneys. Thus Schade contends that, in the presence of alkalies (hydrates), uric acid or its salts may pass into a state in which it is far more soluble than usual. Moreover, on its path to crystallisation from this over-saturated solution, it passes through a _colloid_ stage in which it is relatively stable. The maintenance of this colloid stage and consequently the retardation of precipitation is promoted by certain substances, _i.e._, glycerine, urea, serum, albumen, nucleic acid, etc. But hitherto the therapeutic possibilities suggested have not been invoked. ORGANIC COMBINATIONS It will be recalled that purin bodies cannot be detected in the _blood_ in health, though their administration by the mouth results in an increase in the excreta. Minkowski, to account for this, suggested that the purins in the blood were circulating in a combination which prevented them from giving the usual reactions, typical of their presence therein. We have an analogy in the masking of arsenic and iron in the cacodyl compounds and the ferrocyanide ion.[8] The explanation proffered by Minkowski was elaborated by Von Noorden. His view was that lying at the disposal of the normal organism are a certain number of organic substances. These latter can combine with uric acid and render it soluble. It is then in this form passed through the blood in the kidneys, which eliminate from it the uric acid. Now, in gout these organic substances are deficient or wanting, and the result is that the uric acid is passed into the blood in the form of _urates_, the elimination of which only proceeds with difficulty; in other words, the purins normally circulate in _organic_ combination and abnormally as _salts_ of _sodium_. It is worthy of note that, from a solution containing albuminous substances, Burian and Walker Hall found that while it was easy to remove the bulk of the purins, a certain percentage always remained which it was difficult to extract. The view that uric acid is probably carried in the blood in combination with some other organic body and not, as was formerly supposed, with sodium salts, rapidly gained adherents, but the nature of the organic complex is still not accurately known. Many believe that at least a moiety of the uric acid circulates in combination with _nucleic_ (thyminic) _acid_, but no such compound has yet been isolated from the blood. Nevertheless, as MacLeod suggests, this theory, were it proved correct, would account for the fact that some purins at least are katabolised in the body when they are given in a combined state, as _thyminic acid_, but are excreted unchanged when ingested in a free state. Thus, certain purins, _e.g._, _adenine_, when given freely, cause inflammation and calculous deposits in the kidneys of dogs which, however, does not ensue when they are fed with thymic acid.