262 Dr. Burneti’s Reviews and Abstracts 
Ill. New Muscle-element in the Thoracic Muscles of Insects. 
Aubert* states that he has found an entirely new form of mus- 
cle-element in the Libellulide ; this consists of flat, primitive, 
muscular bands occurring only in the thorax, and which by means 
of a pitcher-shaped (becherformigen) apparatus, move the wings. 
The following are his conclusions on this subject : 
“1. The comparatively very large muscles of those insects 
which fly with a buzzing sound, separate, when fresh, into fine, 
transversely striated fibres. 
2. fibres are the primitive muscular fibrille. : 
3. Between the fibrille there isa granular mass, the use of 
which is unknown. * 
A. All other muscles when fresh present no appearances of this 
ind. 
5. The Libellulide have in the thorax primitive muscular 
ands. 
6. The elements of the muscles are little cakes or cylinders 
which are applied together, forming the fibrille 
7. During contraction, the fibrille thicken, and the strie are 
approximated.” 
These results have been confirmed by my own experience, for 
the thoracic muscles of insects have long been to me beautiful ob- 
jects for the study of the histological elements of muscular tissues. 
It is a form of this tissue particularly to be recommended for the 
study of the intimate sarcous elements. The fibrille readily 
separate into the discs of which they are composed, and the 
whole field is then filled with these last floating freely about. 
But it is a question if these primitive fibrilla which are here so 
distinct, are not the products of definite cleavages of primitive 
muscular fibres. In studying them carefully with a power of 
800 to 1000, we have been able to detect no remains of their 
early formative conditions. Furthermore, we know that the 
muscular fibre is the primitive embryological element of this tis- 
sue. It therefore appears to us. probable that this peculiarity of 
the thoracic muscles of insects is due simply to readiness for 
cleavage, and which may be subservient to their rapid and deli- 
cate action. 
Another point which we have noticed, and which Aubert also 
has alluded to, is the singular spiral aspect which these fibrille 
sometimes asstime from an apparently irregular movement in their 
contraction. This is particularly worthy of note now, since, re- 
cently, Martin Barry (Miiller’s Arch. 1850, p. 529) has advanced 
the doctrine of the spiral structure of muscular fibrilla. We have 
not critically examined the ground on which Barry has 2 
* Ueber die eigenthiimliche Structur der Thoraxmuskeln der Insekten, in Sie 
bold d: Kélliker’s Zeitsch. fiir Zool. iv, 1858, p. 888, Taf. xv. ae 
