BOOK I. CHAP. IX.] THE CONTRACTILE TISSUES. 311 



it is also true that they are exhibited in dead tissue, and that 

 they often seem to depend upon a diluted state of the sarcode 1 . 



It soon became apparent that the most remarkable properties 

 of sarcode, or, as it is now termed, protoplasm, were not peculiar to 

 it. Siebold 2 discovered contractile powers in the yolk-spheres of 

 Planarian ova, and Wharton Jones 3 in the white corpuscles of 

 vertebrates, while Kiihne 4 contrasted muscular tissue, Amoebae and 

 Vorticellae in respect of their excitability and death-changes. Thus 

 the way was prepared for the doctrine of the analogy of sarcode 

 to the body or contents of the animal cell, and the doctrine of 

 the cellular nature of infusoriarjs 5 ; from which we derive the unity 

 of the contractile power in such creatures as the Amoeba and in 

 the specialized muscular tissues of man. 



Limited powers of contraction are enjoyed by very many cells 

 of the bodies of higher animals. The connective-tissue corpuscles 

 of the cornea 6 , the cells of hyaline cartilage 7 , and the walls of 

 capillaries 8 , seem capable of contracting, at least when stimulated 

 by electrical currents. The gliding motion of granules in the pigment 

 cells of the frog's skin may be readily demonstrated. White blood 

 corpuscles and lymph cells exhibit movements in no respect different 

 from those of primitive sarcode; while ciliated epithelia and sper- 

 matozoa offer the simplest examples of movement as a specialized 

 function. But it is in muscles that contraction becomes prominently 

 the function of the tissue, and where its laws have been most fully 

 examined. 



ciassifi- Of muscles there are, from the histological point of 



cation of view, three sorts : (1) the smooth involuntary muscular 



tissue of - intestines > uterus, arterial walls, &c. ; (2) the 

 striated muscles of the general voluntary system ; and 

 ture. (3) the striated involuntary muscle of the heart. 



Structure of unstriped involuntary muscle. 



This variety of muscular tissue consists of innumerable small 

 fibre-cells (0'045 to 0'230 x 0'004 to O'Ol of a mm.) extended in 



1 Kecklinghausen, " Ueber Eiter- und Bindegewebs-Korperehen." Virchow's Archiv 

 f. path. Anat. u. Physiol., Vol. xxvin. p. 166, 1863. 



2 Siebold, Froricp. Notizen, No. 360, p. 85. Quoted by Strieker, "Ueber die Zelle." 

 Handbuch der Lehre von den Gewcben, chap. i. p. 2. 



3 Wharton Jones, "The blood corpuscle considered in its different phases of develop- 

 ment in the animal series." Phil. Trans. Roy. Soc. Lond. 1846, pp. 63106. 



4 Kiihne, " Untersuchungen ii. Bewegungen u. Veranderungen der contractilen 

 Substanzen." Archiv fur Anat. Physiol. u. wiss. Med. (Keichert u. du Bois-Eeymond), 

 1859, p. 816. 



6 M. Schultze, "Ueber Muskelkorperchen und das, was man eine Zelle zu nennen 

 habe." Archiv f. Anat. Physiol. u. wiss. Med. (Eeichert u. du Bois-Eeymond) , 1861, p. 17. 



6 Kiihne, Protoplasma, &c., p. 125. Eollett, Strieker's Handbuch, p. 1103. 



7 Heidenhain, "Zur Kenntniss des hyalinen Knorpels." Studien des physiol. Inst. 

 zu Breslau, Part 2 (1863), p. 1. 



8 Strieker, "Untersuchungen ii. die Contractilitat der Capillareu." Wiener Sitzungsber. 

 d. math.-naturwiss. Classe, LXXIV. p. 313, 1877. 



