238 SUMMARY OF CURRENT RESEARCHES RELATING TO 



continue into the cytoplasmic framework. The nucleus is almost always 

 crowded off to one side of the cell, often touching the edge. In many 

 cases vacuoles separate the centrosphere from the nucleus. The centro- 

 sphere with its centriole seems to be the dynamic centre of the cell. 



J. A. T. 



Reissner's Fibre.— George E. Nicholls (Joimi. Compar. Neurology, 

 1917, 27, 117-90, 35 figs.). Numerous careful experiments on this 

 structure have been made with Selachians. If severed the fibre will 

 generally be withdrawn in both directions from the lesion, the retrac- 

 tion being apparently effected by a spiral winding of the fibre, which 

 attains a greatly increased thickness as the withdrawal proceeds. In 

 dead or dying material this retraction may continue until the whole of 

 the fibre has withdrawn to its points of attachment. In living speci- 

 mens a tangle may be formed at the broken ends. In individual 

 specimens in which such retraction has taken place there is a distinctive 

 reaction — an abnormal posture when at rest, and probably an unusual 

 motion. This reaction becomes apparent very shortly after the return 

 to consciousness in anaesthetized fishes ; it may be intermittent, and it is 

 manifested by different specimens for widely different periods. There 

 is probably a connexion between the degree of the reaction and the 

 extent of the retraction of the fibre. The reaction is not observed in 

 those individuals in which the fibre has been broken, but has, for any 

 reason, failed to retract. Regeneration takes probably not less than a 

 week. It commences with the uncoiling of the fibre, which extends 

 backwards more or less slackly, becomes swollen, and probably by further 

 growth comes once more into contact with the hinder wall of the sinus 

 terminalis (original or secondary) into which it becomes inserted. It 

 would appear that, as suggested by Dendy, the fibre serves to control 

 automatically the flexure and pose of the body. J. A. T. 



Blood Supply of Areas of Langerhans. — Mary Drusilla Flather 

 {Afiat. Record, 1919, 16, 71-7, 8 figs.). The islets of Langerhans are 

 groups of internally secreting glands embedded in the pancreatic tissue. 

 Islets and pancreatic acini probably arise from common primordia. The 

 cells of the islets, varying in form and structure, are always arranged in 

 cords or masses separated by anastomosing blood-vessels. There is also 

 in the islet a plexus of blood-vessels. The author studied the islets or 

 areas in alligator, opossum, horse, racoon, skunk, badger, rabbit, and 

 guinea-pig. With one exception, only one specimen of each species 

 was studied, but the facts point to a distinct specificity of the cells and 

 blood-vessels. J. A. T. 



Intercalated Discs in Striped Muscle. — H. E. Jordan (Anat. 

 Record, 1919, 16, 203-15, 1 fig.). Evidence is adduced that genuine 

 intercalated discs occur in voluntary striped muscle under certain con- 

 ditions. Support is found for the hypothesis that the intercalated discs 

 of cardiac muscle are in essence modified irreversible contraction bands. 



J. A. T. 



Antiquity of Bone Structure. — Roy L. Moodie {Froc. Amer. Assoc. 

 Anatomists, in Aiiat. Record, 1919, 16, 157). The first bone arose in 



