THE GENERAL CONDITIONS OF LIFE 335 



product of which is the amyloid substance, or because passively 

 they are torn apart, pressed upon, asphyxiated and killed by the 

 substance accumulating in masses. Amyloid metamorphosis is a 

 secondary phenomenon of disease, appearing especially in connection 

 with long-existing, chronic diseases, such as tuberculosis, long- 

 continued suppurations, etc., in the abdominal organs, especially 

 the spleen, liver, kidneys and lymphatic glands. This indicates 

 that nutritional disturbances of the tissues, very gradually developed 

 and profound, cause the cells to be put into the condition where 

 their proteid changes gradually into amyloid substance. Beyond 

 what has been stated, amyloid metamorphosis remains still one 

 of the most enigmatical among the metamorphic processes, al- 

 though it is wide-spread and possesses great importance in 

 pathology. 



Finally, calcification is in a certain sense a counterpart to amy- 

 loid metamorphosis ; for, as in the latter amyloid substance, so in 

 the former lime-salts are formed by 

 the cells, and are either excreted to 

 the outside or deposited in the dying 

 cell-substance itself. The formation 

 of bone in the normal body is analo- 

 gous to the former. Large skeletal 

 bones develop from a cartilaginous 

 basis; the cartilage-cells excrete into 

 the ground- substance calcareous salts, 

 especially calcareous phosphate and 

 carbonate ; particles of these press 

 gradually upon one another blend FlG . 148 ._ Amyloi( ;7e^nerationof the 



together, and thus form the SOlld bony capillaries of the liver ; the cells 



i i ,1 T n are forced apart by the amyloid 



Substance, in Which the bone-Cells masses stored up between them. 



continue to live as so-called bone- 

 corpuscles. This process, which ap- 

 pears absolutely necessary in the development of the vertebrate 

 organism, occurs also under pathological conditions, especially 

 when in old age or after certain diseases the cartilaginous discs in 

 the joints ossify. In these cases the same phenomena are present, 

 excepting that, as a rule, the cells by which the lime-salts are 

 excreted later die. Besides this ossification, there occurs also 

 under pathological conditions a true calcification of the cells 

 themselves, in which the lime-salts become stored within the 

 dying cell, until finally the living substance has wholly disappeared 

 and its place is taken by a cemented calcareous mass. This 

 happens in the walls of the arteries (Fig. 149, A), so that 

 they become brittle and afford an opportunity for haemorrhages ; 

 if the latter take place in the brain they constitute apoplexies, or 

 so-called paralytic strokes. Further, in certain brain-diseases the 

 ganglion-cells of the brain become calcified, and there are 



