PROCESSES OF REPAIR AND NEW FORMATION 



Regeneration. 



By the term regeneration is meant a process' of new formation 

 of tissue which occurs in connection with tissue loss, replacing such 

 loss and then ceasing. 



Renewal by metabolism of the functional capability of cells 

 remaining alive after fatigue and exhausting diseases is known as 

 recovery or rccoiisfitiifioii. In the living organism cellular material 

 is being continually used up and in consequence there are always 

 some cells being destroyed and new ones growing to take their place. 

 The cellular covering of those surfaces which are in relation with 

 the external world and from which the cells are loosened by 

 mechanical influences (epithelium of the skin and mucous mem- 

 branes), is especially subject to continual losses and compensation 

 for such losses by a succession of new cells. In the glands, too, 

 there is apparently a continual change of old and new cells, as the 

 function of the gland cells cannot but occasion in them aging and 

 death ; this exchange is an active one in the tissues of the testicles 

 during the period of seminal production, and in the ovary, too, the 

 formation of ova is in a measure a regenerative production. In 

 some glands which form their secretions without particular destruc- 

 tion of their cells (mammary glands, kidneys, sweat glands), 

 renewal in this sense is, however, not recognizable ; and in case 

 of the important elements of the central nervous system, the 

 ganglionic cells, it is a question whether they are at all subject to 

 change or persist throughout the whole life of the individual. 



The cellular constituents of the blood and lymph are very perish- 

 able, and in the spleen, bone marrow and lymph nodes compensatory 

 production of these corpuscles is unceasingly going on. 



A regenerative process may be regarded as pathological only 

 in the sense that it occurs in connection with unusual losses of 

 substance or pathological lesions of tissues, as after ruptures in 

 continuity ; it is in reality only an exacerbation of physiological 

 histogenesis as the processes of growth in both are identical. 



