1 1 8 REGENERA TION . 



animal five and three-fourths by three and one-half centimetres. The 

 glandular tissue was also found less developed in the control animal. 



In another experiment the rabbit experimented upon bore young 

 when it was six and a half months old. Soon after the birth of the 

 young and before the mamma had been used the animal was killed 

 and the single mamma that had been left was measured. It was 

 much enlarged and projected more than the normal mammae. It 

 measured nine by five centimetres. In a normal control animal 1 the 

 corresponding mamma measured seven by five centimetres. The 

 number of acini was in the proportion of sixteen in the animal oper- 

 ated upon to ten in the normal. The results show a distinct com- 

 pensating hypertrophy, due to a hyperplastic increase in the number 

 of elements of the gland. 



A further example of compensating hypertrophy has been found 

 after the removal of the spleen, when the lymphatic glands of other 

 parts of the body become enlarged. There are also observations 

 which go to show that after the removal of some of the lymphatic 

 glands others undergo an enlargement. 



Ziegler 2 has given a critical review of the various opinions and 

 hypotheses that have been advanced to account for the process 

 of hypertrophy. According to Cohnheim 3 hypertrophy in bones, 

 muscles, spleen, and glands is due to hyperaemia, i.e. increased blood 

 supply. He thinks that neither mechanical nor chemical stimuli can 

 cause directly new processes of growth. Recklinghausen 4 thinks 

 that hypertrophy is not due to any extent to an increase in the food 

 supply. Samuel 5 explains hypertrophy as due to a removal of, or 

 to a decrease in, the resistance to growth and also to the influence 

 of the nerves. Klebs 6 thinks that three factors enter into the prob- 

 lem, (a) inherited peculiarities, (b} overfeeding, (c) a removal of the 

 controlling influences. Weigert believes that reparative processes 

 are due to the removal of influences that prevent growth, and not 

 to a direct stimulus. He thinks that a stimulus may start a func- 

 tional act, but can never start a nutritive or a formative one. Good 

 nourishment, for instance, may bring a tissue to a maximum develop- 

 ment that is predetermined by innate peculiarities, but " idioplastic 

 forces " are not thereby increased. Pekelharing 7 thinks that hyper- 

 trophy is due to a disappearance of a resistance to growth, and also 

 to a stimulus causing proliferation. 



We see from these various opinions how little is really known ; 



1 Not, however, from the same litter. 



2 Internal. Beitrage zu wissensch. Medicin. Festschrift fur R. Virchow, Vol. II, 1891. 



3 Vorlesungen itber allegemeine Pathologic, Vol. I, 1882. 4 Pfandbuch. 



6 Handbuch d. allgem. Pathologic, 1879. 6 Allgemeine Pathologic, Vol. II, 1889. 



7 Uber Endothelwucherungen in Arterien. Beitr. z. pathoL Anat., Vol. VIII, 1890. 



