1 102 MICBOOKYSTALLISATION, ETC. 



the body of Limax. 5. The sinuous lamellae which intervene between 

 the parallel plates of the ; sepiostaire' of the cuttle-fish, the imitation 

 of this being singularly exact. 6. The calcareous concretions that 

 give solidity to the * shell' of the bird's egg, the semblance of which 

 Professor Harting was able to produce in situ by dissolving away 

 the calcareous component of the egg-shell by dilute acid, then im- 

 mersing the entire egg in a concentrated solution of calcium chloride, 

 and transferring it thence to a concentrated solution of potassium 

 carbonate, with which, in some cases, a little sodium phosphate 

 was mixed. 1 Other forms of remarkable regularity and definite- 

 ness, differing entirely from anything that ordinary crystallisation 

 would produce, but not known to have their parallels in living bodies, 

 have been obtained by Professor Harting. Looking to the relations 

 between the calcareous deposits in the scales of fishes and those by 

 which bones and teeth are solidified, it can scarcely be doubted that 

 the principle of ; molecular coalescence ' is applicable to the latter, 

 as well as to the former ; and that an extension and variation of this 

 method of experimenting would throw much light on the process of 

 ossification and tooth formation. The connection of these results 

 with the work of Vogelsang (p. 1096) on globulites and other 

 embryonic crystalline forms is obvious. The inquiry has been 

 further prosecuted by Dr. W. M. Ord, with express reference to the 

 formation of urinary and other calculi. 2 



Micro-chemical Analysis. The methods which serve for the 

 qualitative analysis of chemical substances, and which are based 

 upon the reactions shown by such substances when treated with 

 solutions of various reagents, have been applied by numbers of 

 workers to the identification of the constituents of a material by i IK- 

 aid of chemical reactions, the results of which are traced upon the 

 microscope stage. Thus a very complete scheme has been worked 

 out by H. Behrens for the detection of the constituents of inorganic 

 compounds, 3 and a somewhat similar, although naturally less com- 

 prehensive, scheme has been given by the same author for the 

 identification of organic compounds. 4 The analytical methods arc 

 intended primarily to serve for identifying the components of a 

 material available only in small quantities ; but in many cases the 

 micro-chemical method is more rapidly applied, and is more 

 accurate in its results, than the ordinary processes of qualitative 

 analysis. In applying the microscope for this purpose the substance 

 to be examined is placed upon a watch-glass or glass slide, either in 

 the solid state or in the form of a solution ; the various crystalline 

 forms which make their appearance as a result of the addition of 

 different reagents are then noted, -and from the information thus 

 obtained a knowledge of the constituents of the original substance is 

 deduced. A very important application of micro-chemical analysis 



1 See Prof. Harting's Eecherches (le Morphologic synthetique sur la production 

 artificielle de quelques Formations Calcaireslnorganiques,publiees par I'Acadcni ic 

 Royale Neerlandaise des Sciences, Amsterdam, 1872; and Quart. Joiirn. Microsc. 

 Scl xii. p. 118. 



2 See his treatise On the Influence of Colloids upon Crystalline Frm and 

 Cohesion, London, 1879. 



5 Anleitung zur inikrochemischoi Analyse, Hamburg, 1895. 



4 Mikrochemischen Analyse der organischen VerHndungen, Hamburg-, Lsur>. 



