638 SUMMARY OF CURRENT RESEARCHES RELATING TO 



that their recognition is of fundamental importance. A sinusoid is a 

 sub-division of a vessel produced by intercrescence between its endo- 

 thelium and the parenchyma of an adjacent organ. The proliferating 

 tubules or trabecular of an organ encounter a large vessel and invade 

 its lumen, pushing the endothelium before them. The vessel, on the 

 other hand, sends out branches to circumvent the tubules. By the con- 

 volution or anastomosis of the tubules or trabecular, the large vessel 

 becomes sub-divided into small ones. This is the process of inter- 

 crescence which produces sinusoids. It follows that a sinusoidal circu- 

 lation is either purely venous or purely arterial. To demonstrate it for 

 any organ, it must be possible to state what vessel has been invaded, 

 and thus resolved into an afferent and an efferent system. An essential 

 characteristic — a consequence of the mode of development — is the 

 almost entire absence of connective tissue between the endothelium of 

 the sinusoids and the cells of the adjoining trabecular. Sinusoids have 

 been demonstrated histologically and developmentally in the Wolffian 

 body, myocardium, liver, and pronephros. They possibly occur in gills, 

 but not in kidney nor lungs. They are found in the adults of lower 

 Vertebrates but are regressive in Mammals, and are probably primitive. 



Optic Reflex Apparatus in Cyclostomes and Fishes.* — P. E. 

 Sargent discusses very fully the structure, development, function and 

 ontogeny of Reissner's fibre apparatus in these forms. Only a hint of 

 his results can be given. In Cyclostomes the opiic reflex apparatus is in 

 many respects in a primitive condition, but the relative size of its 

 elements shows it to be of great importance. It is not fully established 

 until the second month of larval life. Judged by the relative size of 

 the elements, the apparatus probably reaches its highest development in 

 Selachians. Its cell nidulus extends on either side of the median plane 

 through the length of the optic lobes, close to the ventricle. The cells 

 are early distinguishable, but do not reach a functional condition until 

 the young attains the free life. In Ganoids the apparatus is not fully 

 established until several days after hatching. The cells, 40 to 100 in 

 number, lie close to the ventricle in the anterior portion of the tectum 

 opticum, and are grouped about the margin of that portion of the 

 ventricle which extends above the posterior commissure. In Teleosts 

 the cells are small and are concentrated in the torus longitudinalis. 

 Unipolar or bipolar in their general outline, they ultimately give rise to 

 three processes, forming three fibre-tracts on each side of the brain. 

 Concerning the physiological value of the apparatus, the author believes 

 that it offers a " short circuit " for the transmission of motor reflexes, 

 by which a reaction may be brought about more quickly than when the 

 impulse is transmitted through the nerve-tracts of the spinal cord. 



Sensory Nerve-endings in Human Tongue.f — Cf. Ceccherelli gives 

 an account of the many forms of nerve dilatations which occur in the 

 human tongue, including some not hitherto described. On the external 

 layer of the papilla? of the corium and in the filiform papilla? and inter- 

 papillary spaces he describes " corymbose " endings, and in the conical 



* Bull. Mus. Zool. Harvard, xlv. (1904) pp. 129-258 (11 pis.), 

 t Anat. Anzeig, xxv. (190-t) pp. 56-69. 



