xii LIST OF ILLUSTRATIONS 



85. Notochordal tissue ......... 72 



86. Transection through the compact bony wall of a human meta- 



carpal bone ......... 73 



87. Longitudinal section of ground bone from the shaft of the human 



femur 74 



88. Isolated bone cell shrunk away from wall of its lacuna . . 75 



89. An Haversian system, including the central canal, several lamellae, 



lacunae and canaliculi 75 



90. Transverse section of Haversian canal, with contents ... 76 

 91. The primary changes in intracartilaginous bone formation . . 80 

 92. A longitudinal section of the two distal phalanges from the finger 



of a five-months' human fetus . . . . . .81 



93. Reconstruction of cartilage into bone . . . . .82 



94. Trabecula of primary enchondral bone, showing a central deep- 

 staining core of calcified cartilage and a peripheral layer of osteo- 



blasts 83 



95. Trabecula of primary bone from the finger of a human fetus . 84 



96. Intramembranous bone formation in the lower jaw of a sheep fetus 87 



97. Smooth muscle cells 91 



98. Smooth muscle cells from the pig's stomach .... 92 

 99. Smooth muscle cells from the wall of the human intestine . . 92 

 100. Smooth muscle cells from the wall of the human intestine . . 93 

 101. Two stages in the histogenesis of smooth muscle, from the wall of 



the esophagus of a pig embryo 94 



102. A group of myoblasts from the heart muscle syncytium of a 48-hour 



chick embryo ......... 95 



103. Cardiac muscle of guinea-pig, showing several branches, cross 



striations (ground membranes) and a number of intercalated disks 95 

 104. Cardiac muscle cells from the pig's heart, isolated in equal parts of 



alcohol, glycerin, and water 96 



105. Cardiac muscle of the human heart; the abundant branches are 



plainly shown . . . . . . . .97 



106. The central portion of the preceding figure, more highly magnified . 98 

 107. Transection of a group of cardiac muscle fibers from a papillary 



muscle of the human heart ....... 98 



108. Developing muscle fibers from the heart of a human fetus at 



seven months ......... 99 



109. Cardiac muscle fibers ........ 100 



110. Diagram of a striped muscle fiber, according to Heidenhain . . 101 

 111. Six-lobed nucleus from the heart muscle of Limulus, showing the 



continuity of the nuciear wall with the telophragmata . . 101 

 112. Seven nuclei, the product of amitotic division, lying in an undifferen- 



tiated mass of sarcoplasm, from the heart of Limulus . . 102 



