Albuminous Substances mid Saline Solutions. 121 



each turn of the channel a separate cascade. At the same time, in the upper 

 reservoir the uncoloured salt solution ascends rectilineally in a thin stream. 



It may be adventured as a suggestion that the serum enters into conjunc- 

 tion with salt so as to become heavier, and that the saline solution, parting 

 with its salt to the serum, becomes lighter. There is no question (when 

 operating with unaltered serum) of any falling out of solution of the albu- 

 minous substances. 



Where, as in the experiments above cited, we set out to obtain evidence of 

 a down draught of serum and an up draught of salt solution, the salt solution 

 employed must contain more than 4 per cent, of salt. For a 4 per cent, 

 solution of salt has a specific gravity equivalent to that of serum (human 

 serum). 



When we want to arrange for the reverse effect — that is, for an up draught 

 of serum into a lighter salt solution, or a down draught of this into serum — 

 we are by necessity tied down to the employment of solutions containing 

 less than 4 per cent, of salt. With these weaker solutions dramatic pseudo- 

 podial interpenetration and very rapid interfusion are not to be expected, and 

 to achieve effects manifest to the eye, we may best (guiding ourselves here by 

 the principles enunciated by Horace Brown) betake ourselves to diffusion 

 cells of conical section. To achieve a visible up draught of serum we 

 require a cell corresponding in shape to the section of an inverted funnel. 



Into such a cell we introduce a layer of coloured serum, and then superimpose 

 a 3 per cent, solution of salt, filling in with this the remainder of the contract- 

 ing cone and also the stalk of the funnel. At the same time, for the purpose 

 of a control, we fill in a second cell, employing here, as our recipient fluid, 

 water instead of salt solution. It will, after the lapse of a few hours, become 

 manifest that the serum is being caught up into the salt solution, and that it 

 is not sensibly diffusing into the water. 



The down draught of a lighter salt solution into serum can — taking here 

 again as our guide the principles of Horace Brown — be made manifest to the 

 eye by employing a diffusion cell of triangular shape, disposed with its apex 

 downwards, and filling into the apex of this expanding cone uncoloured 

 serum, and superimposing coloured 3 per cent, salt solution. 



Passing on now, the following points may bs briefly adverted to : — 



Where serum and salt solution are brought into conjunction, the content in 

 albuminous substances plays a very important part in the'production of the 

 phenomena described above. When we take a series of capillary tubes, place 

 a fiducial mark upon the upper part of the stems, fill in up to that level with 

 a 6 per cent, salt solution, seal up the distal ends of the tubes, and then 

 with a paraffined hair fine pipette superimpose — in the one tube, upon the 



