ITS CHEMICO-PHYSICAL AND MORPHOLOGICAL PROPERTIES 43 



whilst paranuclei!! bodies remain almost unaffected ; on the other 

 hand, the latter become better stained in ammoniacal staining solu- 

 tions, such as ammonia, carmine, etc. Many substances, such as 

 eosin, acid fuchsine, etc., have a greater affinity for paranuclein. 

 Hence it is possible, by using two staining solutions at the same 

 time, to stain the nuclein bodies a different colour from the para- 

 nuclein ones, thus bringing about a so-called contrast staining 

 (fuchsine and solid green, hematoxylin and eosin, Biondi's stain) ; 

 however, since the nature of staining processes is as yet very im- 

 perfectly understood by us, it is not possible at present to lay down 

 general rules concerning the staining properties of these two nu- 

 clear substances. 



I consider that nuclein and paranuclein are the essential constituents 

 of the nucleus, and that its physiological action depends in the first 

 instance upon their presence. They seem to me to be correlated 

 in some way or other. Flemming (II. 10) has suggested, that the 

 nucleoli may consist of nuclein in a special condition of develop- 

 ment and density, thus representing a preliminary chemical phase 

 of it. The material that we have at present for examination is not 

 sufficient to enable us to decide these questions. 



The three other substances which may be distinguished in the 

 nucleus, linin, nuclear sap, and amphipyrenin, appear to me to be of 

 much less importance ; it is possible also that they are not always 

 present. 



The name linin has been applied by Schwarz (II. 37) to the 

 material of which the threads, which frequently form a network 

 or framework in the nuclear cavity, consist ; these threads are not 

 affected by the ordinary staining reagents used for the nucleus, 

 and can by this means, as well as by their different chemical re- 

 actions, be easily distinguished from the nuclein, which is deposited 

 upon them in the form of small particles and granules (Fig. 20 

 A, C). In many respects it resembles the plastin of proto- 

 plasm, and indeed Zacharias has called it by that name. 



Nuclear sap may be present in larger or smaller quantities ; 

 it fills up the interstices left in the structures composed of nuclein, 

 linin, and paranuclein. It may be compared to the cell-sap which is 

 contained in the vacuoles of the protoplasm, and no doubt functions 

 in a similar manner, by nourishing the nuclear substances, just as 

 the cell-sap nourishes the protoplasm. By the action of several 

 reagents, such as absolute alcohol, chromic acid, etc., finely granu- 

 lar precipitates are caused to make their appearance in the nuclear 



