47 
The tissues undergoing most change are the epithelium and the 
blood. The epithelial cells are almost invariably enlarged, most 
markedly in the sub-skeletal regions. In the hard condition these 
cells are small, not well defined, and graduate into the connective 
tissue cells. But at the period of ecdysis they are much enlarged, 
arranged in a regular layer, and are in a state of considerable meta- 
bolic activity.^ The periphery of the cell in each case is very 
distinct, except externally where the secretion is taking place. 
The epithelial cells of the digestive and excretory organs are 
similarly enlarged, so much as to appreciably diminish the lumen 
of the tubules. The only assignable cause for this distention in the 
latter case, at all events, is that the cells are preparing to proliferate. 
The extraordinary vitality displayed by the epithelium at this 
period is sustained partly through the agency of the subjacent con- 
nective tissue cells. The latter are utilised as transformers, and for 
the purpose of storing reserve material mainly in the form of 
glycogen. That variety of the connective tissues which forms a 
parenchymatous envelope for the intestine carries out the same 
function, and the other general connective tissues in a lesser degree. 
The muscular tissue is at first perplexing on account of the fact 
that certain muscular fibres show marked change while others again 
are in a normal condition. On discrimination it appears that all 
voluntary muscles are aft'ected, whereas some of the involuntary 
ones are not changed. The large fibres of the muscles of the limbs 
lose their pronounced margins, and have the appearanceof a some- 
what homogeneous mass with very dull and ill-defined striations. 
The septal zones are not so clear, though the latter is possibly 
an optical effect due to the former. It is known that myosin 
which is soluble in salt solution constitutes the main part of the 
interseptal zone. On treating muscle with salt solution, the inter- 
septal zone becomes transparent and loses its polarising property, 
owing to the solution of the myosin. This is apparently what takes 
place in the natural course of events in the case of the voluntary 
muscles of the crab at the period of ecdysis. Enclosed in their 
thin investments of endomysium, they are freely bathed in the 
blood. The salt in solution in the blood appears therefore to act 
upon the fibres dissolving the myosin, probably producing myosin- 
ogen, which is held in solution. The effect is as noted above, the 
loss of the interseptal pigment, and an accompanying fluidity of the 
fibres. This is what I consider enables the muscles of the limbs to 
4. — According to Vitzou. 
