158 REPORTS ON THE STATE OF SCIENCE.—1918. 
Many animal organs behave exactly like gels when immersed in 
water and swell enormously. This swelling is affected by the 
presence of small proportions of acids, alkalies or salts in the water. 
Thus, in the vase of gelatin, fibrin and egg-albumin, acid solutions of 
moderate concentration greatly increase the amount of swelling and 
the amount of water absorbed by the organicsubstance. This is due 
to the presence of free hydrogen ions. On the other hand, the 
addition of a suitable alkali or salt will reduce the swelling and 
restore the substance to its previous condition, by neutralising the 
excess of free hydrogen ions. If an excess of hydroxl ions be 
added in the attempt to reduce the swelling, the gel may be peptised 
and “dispersed.” A typical glaucomatous state may be induced in 
sheep’s eyes in vitro by immersing them in very dilute hydrochloric 
acid. The normal condition may be restored by the addition of 
ferric chloride or other appropriate salts. Precisely the same 
phenomena are observable with living tissues, both in health and 
disease, and any desired colloidal condition may be obtained in the 
latter by appropriate colloidal treatment. Thus, the administration 
of salt has been successfully employed in the treatment of nephritis 
and cedema.4 ‘The extensive use of salines solutions in various 
stages of collapse has long been practised in all civilised countries, 
and its success is due to the action of these substances on the 
colloidal serum. Such salts prevent the swelling and coagulating 
effects of the acids formed in the diseased tissues, just as they 
decrease the effect of other acids, or effect the precipitation of 
certain colloids in vitro. 
Inflammation is also a colloidal phenomenon, and is brought 
about by precisely similar conditions in the living subject, and in 
artificially prepared plates of non-living materials.® It is easy, for 
example, to produce “artificial flea bites’’ by pricking a piece of 
gelatin with a needle dipped in formic acid and then placing the 
gelatin in water. The remedy—injecting into the swollen portion 
sufficient alkali to neutralise the acid—is as efficient as when this 
method is applied to a real bite. The complete comparison of these 
“bites” with the phenomena observed when a flea bites the human 
subject is, however, a very difficult matter. 
The unknown substance which produces goitre’? is most probably 
colloidal in nature. Hence, from one point of view, therapeutics is 
largely concerned with a study of the formation of colloids which 
are abnormal in the sense that they do not occur in the natural 
processes of a healthy body, but which—when regarded as colloids— 
are no more unusual than the coagulation of a highly dispersed sol 
or the peptization of a coarser gel. he chief difficulty in the way 
of experiment or treatment is that in one case conditions are severely 
restricted owing to the fact that the colloids form part of a living 
organism. 
4M. H. Fischer, @dema and Nephritis, New York, 1915. 
5A. Oswald, Zeitsch. f. exp. Pathol. wu. Therapie, 8, 226, 1910; Koll. Zeit. 9, 251 
(1911). ; 
6M. H. Fischer, @dema and Nephritis, New York, 1915, pp. 199, 602. 
7H. Bircher, Hrgebnisse der Chirurge u, Orthopedic, 5, 133 ; Zeits. f. exp., Pathol. 
9, etc. 
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