Under the data of the catalogue of profiles of HI line absorption, obtained on the radiotelescope RATAN-600 together with outcomes of other authors, large-scale structure of cold interstellar gas is found in the spiral arms of Galaxy.
In general these structures are parallel to the axes of a spiral arms. Their diameter in a transversal direction is 100 pc, and there are 4-5 such structures on a line of sight inside the arm. It was supposed, that these formations could be connected with the pulsing character of clouds formation at the front galactic impact waves.