Alveolar Cells from Mammals 



245 



are often met with the pictures of cristae. More 

 frequently, however, the boundaries of these cristae 

 are not parallel but have narrow passages. 



Osmiopliilic bodies (tig. 2), first described under 

 the name of ""Plasmasome'" by Kisch (5) and by 

 various authors, are permanent structures pertaining 

 to the large alveolar cells. They have two aspects 

 depending on their state of completeness. When 

 entire they are oval, with a size of 0.9 micron along 

 the major axis. They consist of laminated or tubular 

 elements with very dense outer limits, the middle 

 region being less dense. 



The thickness of the lamellae for sheets) is about 

 250 A, corresponding to that of the mitochondrial 

 cristae. Moreover, the dark limits are often joined 

 together, as those of the mitochondrial cristae. The 

 structural elements are very often concentric and 

 scaled or folded. They are sometimes parallel, rather 

 like the mitochondrial cristae. 



The various observations mentioned above prompt 

 us to suggest that osmiophilic bodies are derived 

 from mitochondria. The cristae could have become 

 more frequent and elongated, laden with lipids which 



had possibly come from the partial decomposition 

 o\ the mitochondria; this would account for the 

 electron density after osmic fixation. We also think 

 that these bodies can come out of the cell, because 

 free bodies have been observed outside the cyto- 

 plasm. 



When the osmiophilic bodies are incomplete, they 

 make the bounds of a transparent cavity in the cyto- 

 plasm: this cavity is carpeted with some dense frag- 

 ments which are the remains ol the whole body. These 

 cavities perhaps correspond to the vacuoloids which 

 are observed with the light microscope in certain 

 alveolar cells. In this condition they reach or exceed 

 1 micron in diameter. 



The (ioti;i apiniratiis consists t)f little groups of 

 lamellae or tubules, similar to the endoplasmic 

 reticulum. They are joined close together in parallel 

 bundles, very often in contact with one or several 

 small vacuoles. Small dark granules are not very 

 numerous in these regions. In the cell, the Golgi 

 apparatus is scattered in the form of small groups 

 around the nucleus, which are separated by cyto- 

 plasm, mitochondria or osmiophilic bodies. 



^ 



t 



V 



t 



Er 





^ I/' 



Ga 



N 



-*kV 



Ga 



1 micron 



Ji 



f 



.«;• 



Fig. 3. Large alveolar cell in the course of its histiocytic transformation. Rai lung 48 hours after injection of colloidal 

 silica. Modifications of mitochondria (M). Presence of ergastoplasm (Er). Paris of Golgi apparatus (Ga). Nucleus (N). 

 Magnification x 14,000. 



