212 EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 



1. To the enlargement of the cells of which they are composed, 

 which finally assume 90 times their original length, and 12 times their 

 original width. 



2. To the change of the membrane, which is at first tender and ho- 

 mogeneous, and finally becomes covered with pores ; this change occur- 

 ring sooner in the smaller vessels than in the large, where, moreover, 

 it continues to present a transitory organization under the form of a 

 spiral band. 



3. To the multiplication of the great vessels, which takes place from 

 8 to 12 by the division of some of them, which division is effected by 

 the formation of longitudinal dissepiments, dividing them into two or 

 more parts. 



The formation of vessels in general can then be reduced to the fol- 

 lowing points : 



1. The cell of the vessel at first appears under the form of a cell, 

 with very delicate walls, the membrane composing which is perfectly 

 homogeneous, and has not the least trace of striae or any fibrous tissue. 



2. Upon the interior of this delicate membrane there is sooner or 

 later deposited, in the form of superimposed rings of spiral fibres or 

 reticulated lamellae, a second layer of analogous or identical composi- 

 tion, or indeed the fibrous tissue, in consequence of the subsequent 

 deposit of similar material, passes from the spiral to the reticular form. 

 Simultaneously with this internal deposit, a formation of similar layers 

 on the external surface occurs from the thickening of the walls of the 

 contiguous elementary organs, and which determines the disposition of 

 the perforated places. 



Finally, the secondary membrane does not begin to be formed until 

 the cell of the vessel has nearly reached its full development. 



Pay en on the occurrence of Crystalline Deposits in the Tissues of Vegeta- 

 bles. A short notice relative to Payen's observations on the occurrence 

 of crystalline deposits in the tissues of vegetables was given in our first 

 volume ; but as the subject is one of considerable interest, especially 

 with reference to the mode of secretion of inorganic crystallizable mat- 

 ters in living bodies ; and as the facts observed by Payen relative to the 

 manner in which this secretion occurs in vegetables, appear to bear 

 some analogy to those which have lately attracted attention with respect 

 to the secretion of salts and other inorganic matters, by the mucous 

 membranes of animals, we have thought it would not be uninteresting 

 to give a more complete abstract of the results of Payen's observations, 

 taken from a report upon his memoir, by M. Mirbel, in the Annales des 

 Sciences Naturelles, December 1841. 



Previously to Payen, M. Meyen had observed, under the epidermis of 

 various species of fig, masses of crystallized mineral substances, sus- 

 pended by a cellular cord in the interior of large utricules ; but Meyen 

 was deceived in some respects in what he saw. He conceived that the 

 crystallized mass contained a thick kernel of gum, and that the crystals 

 of mineral matter enveloped this kernel, an error which he would not 



