5 86 



NATURE 



{April 22, 1 88c 



especially to horses. But when the tunnel is entirely 

 cleared out and there are no more dynamite explosions, a 

 current of air will set in ; and as there are only 3 kilo- 

 metres more than at Mont Cenis, there is no reason why, 

 in respect of ventilation, it should be more dangerous. 



We may therefore confidently utilise this magnificent 

 way of communication, and be proud of living at the 

 period during which it has been opened. 



Geneva Adolphe GAUTIER, Engineer 



COLLOIDS 



The Influence of Colloids upon Crystalline Form and 

 Cohesion. By W. M. Ord, M.D. (London : Stanford, 



1879) 



THE series of researches which Dr. Ord has put into 

 the hands of the public in the volume before us 

 possess a double value, as dealing with problems in 

 molecular physics of the deepest intere t to the physical 

 investigator and of the highest importance to the surgical 

 practitioner. 



The starting-point of Dr. Ord's work is to be found in 

 very remarkable research made more than twenty years 

 ago by Mr. George Rainey, on the spherical forms 

 assumed by carbonate of lime and other crystalline 

 substances when deposited in the midst of gummy or 

 colloidal liquids. The process by which this assumption 

 of a globular form is effected Mr. Rainey termed "mole- 

 cular coalescence." He also assigned the name of 

 "molecular disintegration" to another process by which 

 the conditions are reversed, and which breaks up the 

 spheres into forms possessing a structure more nearly 

 approaching a crystalline character. The most impor- 

 tant of his deductions was undoubtedly the conclusion 

 that the rounded forms of organised bodies depended on 

 physical and not on so-called vital conditions. If solu- 

 tions of gum arabic (containing malate of lime) and 

 concentrated carbonate of potash are placed together in 

 a bottle with as little mixing of the two as possible, the 

 most perfect microscopic spheres are slowly deposited. 

 They exhibit both concentric and radial markings, and in 

 polarised light present a distinct "cross." They consist 

 of carbonate of lime for the most part, but inclose portions 

 of gum also. When plunged into stronger solutions of 

 gum these spheres lose their globular arrangement and 

 break up into radial lines, and subsequently into smaller 

 particles. This is Mr. Rainey' s fundamental fact; and 

 others entirely analogous have been observed by Harting. 

 Guthrie, and Montgomery, with different substances, and 

 by somewhat different processes. Mr. Rainey was or 

 opinion that these artificial spheres were the exact ana- 

 logues of the globular masses detected by the microscope 

 in bone, shell, in the testa of crustaceans, as in the tail 

 of the shrimp, for example, and in ossified tendons, and 

 he proceeded to argue that by a purely physical process 

 in which the colloidal environment was concerned, not 

 only bone, but starch granules and even the crystalline- 

 lens of the eye were formed. To these fundamental 

 experiments Dr. Ord has himself contributed parallel 

 observations on the disintegration of crystals of uric acid, 

 carbonate and oxalate of lime, murexide, &c, which, when 

 inclosed in gelatin, glycerine, or glycerine jelly, lose their 

 sharpness of outline and transparency of substance, and 

 progress by degrees towards the spherical form. 



Dr. Ord now points out the very important relation 

 held by these obscure molecular processes to the produc- 

 tion of spherical and spheroidal concretions of calcareous 

 matter in the renal and urinary organs, and he has sought 

 to establish this relation by two lines of investigation : 

 (1) by microscopic observation of calculi and other urinary 

 deposits obtained under certain morbid conditions ; (2) 

 by synthetically obtaining identical forms from the various 

 salts, phosphates, urates, &c, in the presence of colloids 

 under varying conditions of temperature and hydration. 



The substances thus investigated were uric acid, urates, 

 oxalate of lime, phosphates, and carbonates ; and the 

 colloids employed were gum, gelatin, albumin, grape-sugar, 

 starch, &c. The experimental results were throughout 

 compared with the microscopic observations of Thudi- 

 cum, Beale, and Prout, and a very large proportion of 

 the forms observed in nature were artificially reproduced, 

 thus affording pregnant suggestions as to the varying 

 circumstances which prevailed in their natural production. 

 Many of these comparative observations are of considerable 

 interest. Thus we learn, on p. 55, that the collospheres 

 of uric acid are always very small and homogeneous when 

 deposited in urine, though they are rare ; and a " dumb- 

 bell" form is still rarer. Both are found in albuminous 

 urine of small density. The experiments with watery 

 solutions of egg-albumin always gave large and brilliant 

 spheres. The conclusion is that the presence of small 

 quantities of urea may retard the formation of the collo- 

 spheres of uric acid. This supposition is strengthened 

 by the known effect of urea in small quantities in modi- 

 fying the crystal form of chloride of sodium. Another 

 deduction is of equal moment. Two-thirds of all urinary 

 calculi are composed of, or start from, a nucleus of uric 

 acid. This uric acid would be quite unlikely to cohere in 

 globules without the presence of a colloidal body — the 

 mucus which would undoubtedly be present. " To make 

 calculi of uric acid without colloids would be as hopeless 

 a task as making ropes of sea-sand." This should be 

 remembered in attempting to prescribe a regimen for 

 suspected calculous disease. Whenever the urine is for 

 any length of time purulent and ammoniacal, the forma- 

 tion of calculus is to be looked for. This conclusion is 

 confirmed by a case given in detail by Dr. Ord, in which 

 paralysis led to renal disease, and which he sums up as 

 follows : — " First comes the paralysis leading to retention; 

 retention permits decomposition and the formation of 

 carbonate of ammonia ; then come cystitis and the 

 mixture of mucus and albuminous fluid with the triple 

 phosphate and the spherical urates ; and so a calculus 

 is formed." Some of the calculi figured by Dr. Beale— 

 notably those of dumb-bell form — were experimentally 

 found to be reproduced by a scarcely suspected substance 

 —oxalate of lime. It was further shown that pre-existing 

 crystals may be resolved into dumb-bell forms in two 

 ways : either by the formation of a dumb-bell within the 

 crystal, or by a disintegration of the crystal and its 

 subsequent conversion in mass into a non-crystalline, 

 homogeneous dumb-bell. 



Catching at a suggestion of Rainey's that [the peculiar 

 action of the colloid resulted from its viscosity, Dr. Ord 

 conceived that some independent evidence for or against 

 this notion might be afforded by the influence of the 

 apparent viscosity of the magnetic field. Without 



