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muscular tissue, some smaller bundies of fibres are fouud having 

 a more special function. 



• The muscles of the jaw interest us mostly; Brandt has descri- 

 bed their direction and origin very miuutely. The contraction and 

 relaxation of these fibres produce a sawing movement of the jaw. 



The histological structure of the muscular fibres may be studied 

 in praeparations , where the connective tissue is macerated by 

 concentrated hydrochloric acid and afterwards put into 0.6 pro- 

 cent salt solution. 



The muscular fibres of Hirudo consist of a contractile envelop 

 constructed of fibrills and sarcoplasm which contaius the nuclei. 



On my plate especially in fig. 8. 9 aud 10 transverse sections 

 of muscular fibres are represented and it may be observed how 

 the fibrills are placed on the circuit and enclose the sarcoplasm 

 in the centrum. 



The terminal ramifications of these fibres want a closer descrip- 

 tion ; the sarcoplasm extends as far as the larger ramifications, 

 while the smaller ramifications consist only of fibrills. 



Apathy has described those fibres so acurately , that it is of 

 no need to repeat it. 



Before leaving the description of the general structure of the 

 head , I wish to say something about the place of the glands. 

 A great number of irregular spaces is found especially in the 

 anterior part of the body, which are filled with unicellular glands. 



Under the epidermis those glands are to be considered as found 

 betweeu the bundies of muscles, which serve to moisten the sur- 

 face of the body, while the glands round the oesophagus and 

 those rouud the pharynx have an other function. These mucous 

 glands have a fine granular contents as is to be seen in my fi- 

 gures (fig. 13, 14 and fig. 1). 



Fig. 1 shows the place of the various glands and at the same 

 time we should observe that the glands round the oesophagus are 

 of a greater size generally; they are meant, when is spoken of 

 the salivary glands of the Hirudinea. 



The unicellular olands are to be considered as modifications of 



