52 THE PHASES OF 



uoles, a net-work is established, which represents a later phase 

 of development of protoplasm. The more coarse, yellow, and 

 shining, and the more densely arranged the points of intersection 

 of the living reticulum are, the nearer it is to its yonth ; on the 

 contrary, the more delicate, devoid of color and luster, the gran- 

 ules are, the more advanced is the age of the protoplasm. That 

 under certain circumstances the living matter in the proto- 

 plasmic lump, by endogenous formation, reproduces its own 

 kind, is proved by observations of older amoebae. Here the 

 coarse granules are newly formed living matter in a juvenile 

 condition. 



With this explanation we can easily understand the differ- 

 ences of age in the elements of tissues, described above. The 

 originally homogeneous lump of protoplasm, with increase of 

 size, is transformed in its peripheral portion into a net-work, 

 whereas the central portion, the nucleus, remains homogeneous. 

 Next a differentiation into a frame- work, and in turn into a net- 

 work, takes place in the central lump, the nucleus, so as to leave 

 smaller, compact centers, the nucleoli. This condition furnished 

 the scheme of the " cell" of the authors. 



At last the differentiation into a net-work has involved the 

 whole protoplasmic body. At this stage no nucleus, and later 

 on even no nucleolus, is perceptible, for the whole body is split 

 up into a reticulum, with coarser and finer points of intersection, 

 and this condition immediately precedes the formation of a basis- 

 substance. 



The living matter passes through these stages, not only in the 

 normal, progressive development of all tissues, but, as I will 

 demonstrate later, also in the process of inflammation, though 

 here in a reversed manner. 



The first assertions as to a difference of the nuclei depend- 

 ing on age are made by Th. Schwann.* According to this author, 

 the nuclei in the juvenile condition are solid, later become hol- 

 lowed, and at length completely disappear, or are absorbed. S. 

 Strieker t maintains that the nucleus of the first globule of seg- 

 mentation originates in the protoplasm, and that the nucleus in 

 its youth represents a lump, while with advancing age it may be 

 transformed into a vesicle. 



* Mikroskop. Untersuchungen iiber die Uebereinstimmung in der Struetur 

 und dem Wachsthum der Thiere und Pflanzen. 1839. Pages 205 and 211. 



t Handbuch der Lehre von den Geweben. Art. " Allgemeines iiber die 

 Zelle." 1868. Page 24. 



