DESCRIPTION OF PLATES 221 



FIGURE 74. Two mast cells lying close to capillaries of the skin (corium). 

 Illustrated to show size and coloration of the granules and length of the 

 cytoplasmic processes of the mast cells. Skin excised on eighth day of 

 typhus. 1,200 diameters. 



PLATE XXX 



FIGURE 75. Photomicrograph of a part of the field drawn in Plate XXVII, 

 figure 65. To show clump of rickettsia. 2,000 diameters. 



FIGURE 76. Capillary, cerebral cortex of guinea-pig 14 inoculated with 

 viscera of Louse W 223, Box 19. (See protocol, page 70.) To 

 show rickettsia in endothelial cells. See low power photomicrograph 

 in Plate XXXI, figure 77. 2,000 diameters. 



PLATE XXXI 



FIGURE 77. Cerebral cortex of guinea-pig 14 inoculated with the viscera 

 of Louse W 223, Box 19. (See protocol, page 70.) Photomicrograph 

 to show early vascular lesion. Approximately 600 diameters. 



FIGURE 78. Photomicrograph of field shown in drawing, Plate XXVIII, 

 figure 69. To show rickettsia in endothelial cells in an early vascular 

 lesion in brain of a guinea-pig. 2,000 diameters. 



PLATE XXXII 



FIGURE 79. Photomicrograph of the field drawn in Plate XXVIII, figure 

 68. To show rickettsia in an endothelial cell. Artery of skin. Autopsy 1, 

 death on tenth day. 2,000 diameters. 



FIGURE 80. Photomicrograph of the field drawn in Plate XXVII, figure 67. 

 To show minute forms of rickettsia in an endothelial cell in situ. Au- 

 topsy 1, death on tenth day. 2,000 diameters. 



FIGURE 81. Photomicrograph of upper part of the field drawn in Plate 

 XXVII, figure 66. To show rickettsia in an endothelial cell. These 

 are the large paired rickettsia. Autopsy 1, death on tenth day. 



FIGURE 82. Photomicrograph of arteriole drawn in Plate XXIX, figure 71. 

 The arrows point to rickettsia. Note the pair of large forms. Autopsy 

 14, death on tenth day. 1,500 diameters. 



FIGURE 83. Photomicrograph. Artery of skin. Autopsy 32, death on 

 fourteenth day. Rickettsia in endothelial cell. This cell lies at the base 

 of a mural thrombus shown at low power in Plate XIII, figure 37. 

 2,000 diameters. 



FIGURE 84. Photomicrograph of a part of the field drawn in Plate XXVI, 

 figure 62. Skin. Mexican typhus. Rickettsia in endothelium in pre- 

 capillary arteriole. 2,000 diameters. 



