22 SUMMARY OF CURRENT RESEARCHES RELATING TO 



that linin forms the ground substance both of chromatin ard oedematin. 

 He thinks that linin occurs in the latter only, the chromatin forming a, 

 continuous network, and not a collection of granules. 



The relation of these results to Heidenhain's cj to-mechanical theories 

 is then considered. The author rejects Heidenhain's theories, especially 

 his law of tension (Spannungs-gesetz), and seeks to replace them by a 

 dynamical theory. The fibrillar are the great mechanical organs of the 

 cell, but they are to be conceived as existing in a certain condition of 

 contraction, which can be increased or diminished by impulses from the 

 microcentre. This is not merely a point of insertion for the fibrillar 

 but is a true centre of force, possessing great complexity, both of struc- 

 ture and function. 



Nucleoli of Central Nerve-cells.* — Herr VI. Kuzicka has found a 

 method for studying the nucleolus, which, he says, is always present in 

 central nerve-cells. It seems that the nucleolus contains several darkly 

 stainable, solid (?) granules imbedded in the lighter nucleolar sub- 

 stance. 



Innervation of Urinary Bladder. | — Dr. N. Griinstein, by means of 

 Ehrlich's method, has studied this subject in the frog and in certain 

 mammals. In the frog, as is well known, the bladder is innervated 

 both from the cerebro-spinal and from the sympathetic system, and has in 

 addition an automatic apparatus composed oflargclor small nerve-ganglia. 

 These consist of nerve-cells and fibres, the former being invested by a 

 pericellular network, and having one or two processes. These are readily 

 distinguished from fibres which have pericellular endings by their struc- 

 ture and staining reactions. These fibres are non-medullated. The other 

 non-medullated fibres are motor nerves, and end in unstriped muscle- 

 fibres ; this has not until now been histologically demonstrated for the 

 urinary bladder. The medullated fibres are of two kinds : first, those 

 with a thin sheath, usually regarded as of sympathetic origin ; second,, 

 the ordinary thick-sheathed cerebro-spinal fibres. The first are few in 

 number, and their origin and importance remains doubtful. The second 

 are sensory, and are furnished with the peculiar end-organs called 

 " trees " by Ehrlich. Among mammals positive results were obtained 

 only in the dog. Here, as in the frog, nerve-ganglia of varying size 

 occur in the bladder- wall. End-organs in the form of trees were demon- 

 strated for the medullated fibres, but they appear to be less complicated 

 than in the frog. 



Structure of Neuroglia.^ — Herr Erik Miiller has investigated this 

 subject in a series of Vertebrate forms from Amjihioxus and Myxine to 

 Mammals. The methods employed were very various. In Amphioxu& 

 and Myxine admirable results were obtained by fixing for 24 hours in a 

 mixture of 1 part of 3 per cent, potassium bichromate and 4 parts of 

 commercial formol, placing for three days in a '6 per cent, solution of 

 potassium bichromate, washing and hardening in spirit, and staining 

 with Heidenhain's iron-hseniatoxylin. For higher Vertebrates, acid 

 alcoholic fixatives gave the best results. 



* Anat. Anzeig, xvi. (1899) pp. 557-63 (1 fig-)- 

 t Arch. f. Mikr. Anat., lv. (1899) pp. 1-11 (I pi ). 

 I Tom. tit. pp. 11-62 (3 pis. and 1 fig.). 



