ZOOLOGY AND BOTANY, MICROSCOPY, ETC 531 



frontals are traversed by a strong artery, or by several, springing from 

 the cranial branch of the cerebral or from its branch, the median 

 cerebral, and uniting in the hood with the branches of the external 

 facial. This peculiarity in the arterial system is connected, not with 

 the peculiar shape of the brain, but with the hood. 



Nutrition of Striped Muscle.* — Nanna Svartz refers to the view 

 that nutriment simply passes from the blood to the tissues through semi- 

 permeable membranes without any specific activity on the part of the 

 cells. Another view is that there are intermediate cells which transport 

 and prepare the nutriment. Following Holmgren, Svartz directs atten- 

 tion to the importance of trophocytes (oenocytes of Prenant, sarcosomo- 

 cytes of Thulin), which are intermediate between the blood and the highly 

 differentiated muscular and nervous tissue. The relation of the tropho- 

 cytes to the various stages of muscular activity is discussed. The 

 appearance of the trophocytes changes so much during the contraction 

 wave that we cannot think of them as remaining indifferent. A direct 

 transference of substances from the trophocytes to the muscle fibres has 

 been seen in many cases, especially when the muscle fibres after con- 

 tration are in need of replenishment. "When the trophocyte has supplied 

 the need of the muscle fibre it shrivels and leaves a few scarcely per- 

 ceptible granulations. 



Physiological Theory of Muscle Contraction.! — H. E. Roaf believes 

 that the contraction of striated muscle can be explained on the hypothesis 

 that lactic acid is set free, and that this combines with protein to form 

 a salt, with a consequent rise of osmotic pressure. Muscle can shorten 

 by osmotic processes until its length is somewhere between 37 and 3 p.c. 

 of its original length. The osmotic process can occur in frog's sartorius 

 in less than • 04 of a second. In order to determine whether all cases 

 can be explained by this hypothesis it is necessary to have measurements 

 of the structures concerned. Insects' muscles, for instance, should be 

 the test as regards the rapidity of contraction. The amount of lactic 

 acid formed during muscle contraction can cause sufficient rise in 

 osmotic pressure to account for the force exerted by muscle contraction. 

 The electrical changes in muscle can be explained by the formation of a 

 protein salt of lactic acid. 



Temperature and Development.:}: — E. D. Sanderson and L. M. 

 Peairs have studied the influence of temperature on the hibernation, 

 aestivation, development, growth, and reproduction of insects. The rate 

 of development within normal limits depends, other factors being equal, 

 upon the temperature. It increases directly with the temperature, the 

 curve for the increase within normal limits being a true mathematical 

 hyperbole. The authors discuss the index of development, the develop- 

 mental zero, the thermal constant, and other technical points. 



* Anat. Anzeig., xlv. (1914) pp. 538-48 (5 figs.), 

 t Proc. Roy. Soc, Series B, lxxxviii. (1914) pp. 139-50. 



X Bull. New Hampshire Coll. Agrio. Exper. Station, No. 7 (1913) pp. 1-125 

 (23 curves). 



2 n 2 



