[macallum] cellular OSMOSIS AND HEREDITY 1ST 



tissue elements to be deposited therein and from these intracellular de- 

 posits to diffuse away again according to tlie needs of metabolism. In 

 this passage from blood vessels into cells, " colloids " diffuse through 

 "■ colloidal " membranes and, as in the case of the casemogen and albu- 

 mins, the only explanation possible thatt the membranes are of such a 

 composition that they dissolve the water-solid phase of the " colloids " 

 (proteins and fats), just as the rubber membrane in Kahlenberg's ex- 

 periments dissolved the copper oleate or the camphor, and passed it 

 through to the other side. 



It is, however, in cells themselves that we see striking evidence of 

 diffusion of colloid through colloid. In the villi during the absorption 

 of fat the epithelial cells convey it to the underlying adenoid tissue and 

 the latter pass it on to the lumen of the lacteal vessel. This transmis- 

 sion is not through the spaces or lacunae of the adenoid tissue, but 

 through the colloidal substance of the adenoid trabecular network 

 stretching between the basement membrane and the wall of the lacteal 

 vessel, and it is transmitted dissolved in this " colloidal '' substance. 

 Indeed, it penetrates the wall of the lacteal vessel only by dissolving in 

 that wall. Even in the epithelial cells covering the villus, a part, at 

 least, of the fat is dissolved in the cell, the protoplasm of which allows 

 it to diffuse readily on towards the basement membrane, but in the 

 lateral membranes of these cells it may be retained in a dissolved state 

 after the cytoplasm has got rid of its charge of fat. 



We know also that in developing nerve cells, the chromatin of 

 [the nucleus diffuses out through the ,membrane of the nucleus to form 

 the substance of the Nissl granules which are so distinctive a feature of 

 nerve cells in adult Vertebrates.^ Further, in the developing ovarian ova 

 of Amphibia, the chromatin of the nucleus alters in composition, gathers 

 in small spherules immediately adjacent to the wall of the nuclear mem- 

 brane and give off material which passes through tlie membrane to con- 

 stitute the,para-nucleoprotedd of the yolk spherules. 



A like diffusion occurs in the hsematoblasts of Amphibia when the 

 antecedent of haemoglobin passes through the nuclear membnane to form 

 haemoglobin in the cytoplasm. In observations conducted by Sutherland 

 Simpson and Hering,^ haemoglobin-like compounds occurred in the cavi- 

 ties of hepatic cell nuclei of the dog which were probably derived from 

 red corpuscles, and some of the latter were observed inside liver cells. 

 Gather intact or in the process of r'egeneration.^ That hœmoglobin can 

 diffuse into the liver cells and into the nuclei follows from the observa- 



^ Scott, Trans. Can. Inst., Vol. 6, p. 405, 1899. 

 "Proceedings Royal Sec, Vol. b. 78 p. 455 190C. 



