522 SUMMARY OF CURRENT RESEARCH ES RELATING TO 



Regeneration of Muscular Tissue in Metamorphosis of Frog.* 

 W. Smirnowa refers to Metschnikoff's observation that during the meta- 

 morphosis of tadpoles, the caudal muscles break down into cells which 

 consist of sarcoplasm with muscle-nuclei. These cells digest the products 

 of the disruption of the muscle and become muscle -phagocytes. 



Smirnowa finds that a portion of the trunk musculature of the larva 

 is also subjected to phagocytosis and complete degeneration. The re- 

 mainder is adapted to the new function of skeletal muscles. The 

 process begins with a disruption of the old muscles, but this stops at 

 different stages and regeneration sets in. The new muscles develop 

 from the nuclei and sarcoplasm of the old muscles. In adaptation to 

 their new function the muscles change their direction and acquire new 

 insertions. 



Development of Connective Tissue.t— Serafino d'Antona has studied 

 in particular the athero-sclerotic thickenings of the aorta. In connec- 

 tive tissue as a whole, he distinguishes (a) the formed elements— cells 

 and fibres— and (b) the un-formed constituents— the matrix and the 

 cement substance. All are enveloped by the nutritive plasma. The 

 matrix, the cement substance, and the fibres, may be called " intercellular 

 substance," but this is a topographical distinction. 



In the aortic thickenings the formation of fibres takes place in two 

 ways. In the one case, they arise in a primitive amorphous substance 

 (metaplasm) independently of any direct relation to the cell-bodies. In 

 the other case, they arise directly from a modified peripheral portion 

 (ectoplasm) of the cell-body. The matrical substance of the fibrils is 

 best regarded as a modified protoplasm or metaplasm, but the author 

 does not exclude the possibility that it may arise in part as excretion 

 products of the cells. The ectoplasm is cell-protoplasm in process of 

 changing into fibrils. 



Whether the first fibrils arise from the metaplasm or from the 

 ectoplasm, they are neither collagenous nor elastic fibres. They are 

 " primitive fibril-structures," on which the differentiated fibres of the 

 definitive tissue are modelled. The collagenous and elastic fibres are 

 stages in developmental processes which have a common starting-point 

 in the " primitive fibril-structures." 



Histogenesis of Cartilage.} — K. von Korff has studied the histo- 

 genesis and structure of the cartilage-matrix in Salamander, Selachian, 

 and Mammals. He finds that the first primordium of the cartilage- 

 matrix, the pre-cartilage or prechondral substance, is not homogeneous, 

 but is composed of acidophilous connective -tissue fibrils which are 

 formed from indifferent connective-tissue cells. After the formation of 

 fibrils, the fibroblasts are changed into pre-chondral and cartilage cells. 



Between the pre-chondral cells the connective-tissue fibrils form a 

 framework of interwoven acidophilous fibrillar strands, the pre-chondral 

 intercellular scaffolding of the cartilage. This increases in mass as the 



* Arch. Mikr. Anat., lxxxiv. (1914) lte Abt., pp. 300-5. 

 t Zeitschr. vviss. Zool., cix. (1914) pp. 484-500 (2 pis.). 

 I Arch. Mikr. Anat., lxxxiv. (1914), lte Abt., pp. 263-99 (1 pi. and 7 figs.). 



