August 24, 1900.] 



SCIENCE. 



303 



ment of the exuvial glands. These are 

 unicellular hypodermal glands, usuallypear- 

 shaped, with the smaller end prolonged into 

 a tube which opens through a pore beneath 

 the cuticula. Sometime before ecdysis 

 these glands begin to grow larger, and the 

 nuclei have well developed membranes with 

 clearly defined chromatin skeins. In the 

 few days immediately preceding ecdysis the 

 glands enlarge rapidly, owing to the secre- 

 tion of an albuminous fluid within the 

 cells, and the nuclei become amoeboid, some- 

 times branching in fine dendritic processes 

 among the globules of the exuvial fluid. 

 The time for ecdysis having arrived the 

 glands pour out their contents gradually 

 until there is a thin layer of the exuvial 

 fluid separating the old cuticula from the 

 hypodermis. The hypodermis now rapidly 

 secretes a new layer of cuticula, and thus 

 the whole animal is covered with this fluid, 

 which enables it to crawl out of its old 

 shell with ease. 



These exuvial glands occur on all parts 

 of the body, but are most numerous on the 

 pronotum. After ecdysis they become 

 small and rounded, with densely staining 

 nuclei . 



The point of interest now is the secre- 

 tion of the secondary layer of the cuticula, 

 which forms the real strength of the in- 

 sect's skeleton. During ecdysis and for a 

 short time thereafter the only cuticula is an 

 extremely thin layer which is easily bent 

 or torn, but about thirty minutes later the 

 deposit on the secondary layer begins and 

 continues until near the middle of the in- 

 star. This layer is often ten times the 

 thickness of the primary cuticula, and 

 seems to be like a cellulose layer, giving in 

 some cases a ' cellulose test.' 



Sugar and Muscl& Fatigue : By Frederic S. 

 Lee, College of Physicians and Surgeons, 

 New Yoi'k. 

 The origin of muscular energy, whether 



from nitrogenous or non-nitrogenous sub- 

 stance, has been disputed. There has like- 

 wise been much discussion over the re- 

 spective parts played by the two recognized 

 causes of muscle fatigue, namely, the de- 

 struction of substance necessary for con- 

 traction and the poisoning of the muscle 

 by so-called fatigue products. Recent ex- 

 perimental evidence both for and against 

 the idea that sugar is an important source 

 of bodily energy has been brought forward 

 by others. The author, together with Mr. 

 C. C Harrold, has studied the problem by 

 experiments on cats which had been put 

 under the influence of the peculiar drug, 

 phlorhizin. It is known that this drug re- 

 moves the carbohydrates from the body. 

 Fasting animals were put under the in- 

 fluence of the drug, were then killed, and 

 the contractile power of the muscles, which 

 continues normally for several hours after 

 death was then tested. The muscles of 

 well-phlorhizinized animals were found to 

 have a contractile power much less than 

 normal, and in this respect resembled 

 muscles in a pronounced state of fatigue. 

 That this result was due to the removal of 

 carbohydrate from the muscles rather than 

 to a mysterious specific action of the drug 

 on the muscle protoplasm is rendered prob- 

 able by the fact that if dextrose be given to 

 an animal that is well under the infiuence 

 of phlorhizin the fatiguing effect of the 

 drug is counteracted and the contractile 

 power of the muscles is restored. It seems 

 to be a legitimate conclusion that nor- 

 mally sugar is a source of muscle energy 

 and the destruction of it a cause of muscle 

 fatigue. 



The supposed connection between the 

 oncoming of rigor mortis and the loss of 

 carbohydrate is confirmed by these experi- 

 ments. A well phlorhizinized animal may 

 begin to go into rigor within five minutes 

 after death, and the rigor is often complete 

 within a half hour. 



